<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-09-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001400482</issuerCik>
        <issuerName>ACUCELA INC.</issuerName>
        <issuerTradingSymbol>NONE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001446698</rptOwnerCik>
            <rptOwnerName>SBI Holdings, Inc.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>IZUMI GARDEN TOWER 19F, 1-6-1 ROPPONGI</rptOwnerStreet1>
            <rptOwnerStreet2>MINATO-KU</rptOwnerStreet2>
            <rptOwnerCity>TOKYO</rptOwnerCity>
            <rptOwnerState>M0</rptOwnerState>
            <rptOwnerZipCode>106-6019</rptOwnerZipCode>
            <rptOwnerStateDescription>JAPAN</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001598959</rptOwnerCik>
            <rptOwnerName>SBI Capital Management Co., Ltd.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>IZUMI GARDEN TOWER 19F, 1-6-1 ROPPONGI</rptOwnerStreet1>
            <rptOwnerStreet2>MINATO-KU</rptOwnerStreet2>
            <rptOwnerCity>TOKYO</rptOwnerCity>
            <rptOwnerState>M0</rptOwnerState>
            <rptOwnerZipCode>106-6019</rptOwnerZipCode>
            <rptOwnerStateDescription>JAPAN</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001598705</rptOwnerCik>
            <rptOwnerName>SBI Investment Co., Ltd.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>IZUMI GARDEN TOWER 19F, 1-6-1 ROPPONGI</rptOwnerStreet1>
            <rptOwnerStreet2>MINATO-KU</rptOwnerStreet2>
            <rptOwnerCity>TOKYO</rptOwnerCity>
            <rptOwnerState>M0</rptOwnerState>
            <rptOwnerZipCode>106-6019</rptOwnerZipCode>
            <rptOwnerStateDescription>JAPAN</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-09-30</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
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                </transactionShares>
                <transactionPricePerShare>
                    <value>8.15</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1485928</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By SBI Incubation Co., Ltd.</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-03-31</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
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                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2036754</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.55</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6196869</value>
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                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By SBI Capital Management Co., Ltd.</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-11-30</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
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                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F6"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
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                <transactionShares>
                    <value>69628</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.72</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1555556</value>
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                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By SBI Incubation Co., Ltd.</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-06-02</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>342500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.08</value>
                    <footnoteId id="F7"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1898056</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By SBI Incubation Co., Ltd.</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-06-03</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>256300</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.63</value>
                    <footnoteId id="F8"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2154356</value>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By SBI Incubation Co., Ltd.</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-06-15</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
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            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1018400</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.30</value>
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                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3172756</value>
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                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
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                <natureOfOwnership>
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                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-06-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>257000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.13</value>
                    <footnoteId id="F10"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
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            </transactionAmounts>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
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                <natureOfOwnership>
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                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-06-17</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
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                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness>
                <value></value>
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                <directOrIndirectOwnership>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
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                <value>2016-06-20</value>
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                <directOrIndirectOwnership>
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        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
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                <transactionShares>
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                <directOrIndirectOwnership>
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        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
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                <transactionShares>
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                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
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                <directOrIndirectOwnership>
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        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
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            <transactionTimeliness>
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                <directOrIndirectOwnership>
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            <securityTitle>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents a transfer of shares of all shares of the Issuer's common stock held by SoftBank Internet Fund, an affiliated entity, to SBI Incubation Co., Ltd., another affiliated entity.  As a result, SoftBank Internet Fund and Soft Trend Capital Corp., the sole general partner of SoftBank Internet Fund, ceased to be beneficial owners of the Issuer's common stock.</footnote>
        <footnote id="F2">This Form 4 is being filed jointly by SBI Holdings, Inc., SBI Capital Management Co., Ltd. and SBI Investment Co., Ltd. Each Reporting Person disclaims beneficial ownership of these securities except to the extent of its pecuniary interest therein, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of all of the reported shares for purpose of Section 16 or any other purpose.</footnote>
        <footnote id="F3">These shares are held directly by SBI Incubation Co., Ltd., which is an indirect wholly-owned subsidiary of SBI Holdings, Inc. SBI Holdings, Inc. may be deemed to be the indirect beneficial owner of these securities.</footnote>
        <footnote id="F4">Represents a transfer of 1,257,252 shares of the Issuer's common stock held by SBI BB Media Investment Limited Partnership, and 779,502 shares of the Issuer's common stock held by SBI Broadband Fund No. 1, both affiliated entities, to SBI Capital Management Co., Ltd., another affiliated entity.  As a result, SBI BB Media Investment Limited Partnership and SBI Broadband Fund No. 1 Limited Partnership ceased to be beneficial owners of the Issuer's common stock.</footnote>
        <footnote id="F5">These shares are held directly by SBI Capital Management Co., Ltd., which is an indirect wholly-owned subsidiary of SBI Holdings, Inc. SBI Holdings, Inc. may be deemed to be the indirect beneficial owner of these securities.</footnote>
        <footnote id="F6">Represents a transfer of all shares of the Issuer's common stock held by Trans-Science No. 2A Investment Limited Partnership, an affiliated entity, to SBI Incubation Co., Ltd., another affiliated entity.  As a result, (i) SBI Transscience Co., Ltd. and (ii) Trans-Science No. 2A Investment Limited Partnership, over which SBI Transccience Co., Ltd. is the sole general partner, ceased to be beneficial owners of the Issuer's common stock.</footnote>
        <footnote id="F7">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $9.34 to $11.14, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the Securities and Exchange Commission (the &quot;SEC&quot;), upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F8">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $9.57 to $9.64, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F9">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $8.98 to $11.42, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F10">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $10.46 to $12.30, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F11">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $10.82 to $13.54, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F12">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $15.08 to $16.41, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F13">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $15.20 to $16.81, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F14">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $15.57 to $16.97, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F15">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $17.61 to $20.23, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F16">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $15.36 to $19.56, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F17">The price reported in Column 4 is a weighted average price.  These shares were purchased in multiple transactions at prices ranging from $20.15 to $22.59, exclusive of any fees, commissions or other expenses.  The Reporting Persons undertake to provide the Issuer, any stockholder of the Issuer, or the Staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F18">Represents a transfer of (i) 1,777,778 shares of the Issuer's common stock held by BIOVISION Life Science Fund No. 1, (ii) 1,871,250 shares of the Issuer's common stock held by SBI Bio Life Science Investment LPS, (iii) 258,582 shares of the Issuer's common stock held by SBI BB Mobile Investment LPS, and (iv) 252,505 shares of the Issuer's common stock held by SBI Phoenix No. 1 Investment LPS, affiliated entities, to SBI Capital Management Co., Ltd.  As a result, (i) BIOVISION Life Science Fund No. 1, (ii) SBI Bio Life Science Investment LPS, (iii) SBI BB Mobile Investment LPS, (iv) SBI Phoenix No. 1 Investment LPS, and (vi) SBI Investment Co., Ltd. (as the sole general partner of BIOVISION Life Science Fund No. 1, SBI Bio Life Science Investment LPS, SBI BB Mobile Investment LPS, and SBI Phoenix No. 1 Investment LPS) ceased to be beneficial owners of the Issuer's common stock.</footnote>
        <footnote id="F19">Represents the transfer of all shares of the Issuer's common stock held by SBI Capital Management Co., Ltd. to SBI Holdings, Inc.  As a result, SBI Capital Management Co., Ltd. ceased to be a beneficial owner of the Issuer's common stock.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Yoshitaka Kitao, Representative Director, President &amp; CEO</signatureName>
        <signatureDate>2016-07-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
