SCHEDULE 13G

CUSIP No.

83356Q108

Names of Reporting Persons

MPC III L.P. (f/k/a Matrix Partners China III, L.P.)

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 8,492,188.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,492,188.00

Aggregate Amount Beneficially Owned by Each Reporting Person

8,492,188.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

9.4 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person: This statement on Schedule 13G is filed by MPC HK III, MPC III, MPC III-A, MPC Management III, MPC III GP (each as defined in Item 2(a) below) and David Su ("Su," collectively, with MPC HK III, MPC III, MPC III-A, MPC Management III and MPC III GP, the "Reporting Persons"). The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G. Consists of 1 Class A ordinary share and 11,039,843 ADSs held indirectly by MPC III (through MPC HK III). MPC Management III and MPC III GP are the direct and indirect general partners, respectively, of MPC III and MPC III-A, and as such, may exercise voting and dispositive power over these shares. Su, a director of MPC III GP, may be deemed to share voting and dispositive power over these shares. This percentage is based on a total of 90,626,150 Class A ordinary shares outstanding as of June 30, 2025, as disclosed to the Reporting Persons by the Issuer.

SCHEDULE 13G

CUSIP No.

83356Q108

Names of Reporting Persons

MPC III-A L.P. (f/k/a Matrix Partners China III-A, L.P.)

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 943,575.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 943,575.00

Aggregate Amount Beneficially Owned by Each Reporting Person

943,575.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

1 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person: The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G. Consists of 6 Class A ordinary shares and 1,226,640 ADSs held indirectly by MPC III-A (through MPC HK III). MPC Management III and MPC III GP are the direct and indirect general partners, respectively, of MPC III and MPC III-A, and as such, may exercise voting and dispositive power over these shares. Su, a director of MPC III GP, may be deemed to share voting and dispositive power over these shares. This percentage is based on a total of 90,626,150 Class A ordinary shares outstanding as of June 30, 2025, as disclosed to the Reporting Persons by the Issuer.

SCHEDULE 13G

CUSIP No.

83356Q108

Names of Reporting Persons

MPC Management III L.P. (f/k/a Matrix China Management III, L.P.)

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 9,435,763.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 9,435,763.00

Aggregate Amount Beneficially Owned by Each Reporting Person

9,435,763.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

10.4 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person: The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G. Consists of (i) 1 Class A ordinary share and 11,039,843 ADSs held indirectly by MPC III and (ii) 6 Class A ordinary shares and 1,226,640 ADSs held indirectly by MPC III-A (in each case through MPC HK III). MPC Management III and MPC III GP are the direct and indirect general partners, respectively, of MPC III and MPC III-A, and as such, may exercise voting and dispositive power over these shares. Su, a director of MPC III GP, may be deemed to share voting and dispositive power over these shares. This percentage is based on a total of 90,626,150 Class A ordinary shares outstanding as of June 30, 2025, as disclosed to the Reporting Persons by the Issuer.

SCHEDULE 13G

CUSIP No.

83356Q108

Names of Reporting Persons

MPC GPGP III Ltd. (f/k/a Matrix China III GP GP Ltd.)

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 9,435,763.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 9,435,763.00

Aggregate Amount Beneficially Owned by Each Reporting Person

9,435,763.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

10.4 %

Type of Reporting Person (See Instructions)

SCHEDULE 13G

CUSIP No.

83356Q108

Names of Reporting Persons

MPC III HK Limited (f/k/a Matrix Partners China III Hong Kong Limited)

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

HONG KONG

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 9,435,763.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 9,435,763.00

Aggregate Amount Beneficially Owned by Each Reporting Person

9,435,763.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

10.4 %

Type of Reporting Person (See Instructions)

SCHEDULE 13G

CUSIP No.

83356Q108

Names of Reporting Persons

David Su Tuong Sing

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

SINGAPORE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 9,435,763.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 9,435,763.00

Aggregate Amount Beneficially Owned by Each Reporting Person

9,435,763.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

10.4 %

Type of Reporting Person (See Instructions)

SCHEDULE 13G

Item 1.

(a)

Name of issuer:

So-Young International Inc.

(b)

Address of issuer's principal executive offices:

2/F, East Tower, Poly Plaza, No. 66 Xiangbin Road, Chaoyang District, Beijing, China 100102

Item 2.

(a)

Name of person filing:

This Amendment No. 3 (this "Amendment") amends and supplements the Schedule 13G originally filed by the Reporting Persons with the United States Securities and Exchange Commission (the "Commission") on February 13, 2020, as amended by Amendment No. 1 as filed with the Commission on February 14, 2022 and Amendment No. 2 as filed with the Commission on February 9, 2024 (collectively, the "Original Schedule 13G"). Only those items that are hereby reported are amended; all other items reported in the Original Schedule 13G, remain unchanged. Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable. Capitalized terms not defined in this Amendment have the meanings ascribed to them in the Original Schedule 13G. Name of Person Filing: MPC III L.P. (f/k/a Matrix Partners China III, L.P.) ("MPC III") MPC III-A L.P. (f/k/a Matrix Partners China III-A, L.P. ("MPC III-A") MPC Management III L.P. (f/k/a Matrix China Management III, L.P.) ("MPC Management III") MPC GPGP III Ltd. (f/k/a Matrix China III GP GP, Ltd.) ("MPC III GP") MPC III HK Limited (f/k/a Matrix Partners China III Hong Kong Limited) ("MPC HK III") David Su Tuong Sing ("Su")

(b)

Address or principal business office or, if none, residence:

Item 2(b) of the Origininal 13(g) is incorporate herein by reference.

(c)

Citizenship:

Item 2(c) of the Origininal 13(g) is incorporate herein by reference.

(d)

Title of class of securities:

Class A ordinary shares

(e)

CUSIP No.:

83356Q108

Item 3.

If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);

(b)

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);

(c)

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);

(d)

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);

(e)

An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f)

An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g)

A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h)

A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:

(k)

Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

Item 4.

Ownership

(a)

Amount beneficially owned:

See Row 9 of the cover page for each Reporting Person and the corresponding comments.

(b)

Percent of class:

See Row 11 of the cover page for each Reporting Person and the corresponding comments.

(c)

Number of shares as to which the person has:

(i) Sole power to vote or to direct the vote:

See Row 5 of the cover page for each Reporting Person and the corresponding comments.

(ii) Shared power to vote or to direct the vote:

See Row 6 of the cover page for each Reporting Person and the corresponding comments.

(iii) Sole power to dispose or to direct the disposition of:

See Row 7 of the cover page for each Reporting Person and the corresponding comments.

(iv) Shared power to dispose or to direct the disposition of:

See Row 8 of the cover page for each Reporting Person and the corresponding comments.

Item 5.

Ownership of 5 Percent or Less of a Class.

Item 6.

Ownership of more than 5 Percent on Behalf of Another Person.

Not Applicable

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.

Not Applicable

Item 8.

Identification and Classification of Members of the Group.

Not Applicable

Item 9.

Notice of Dissolution of Group.

Not Applicable

Item 10.

Certifications:

Not Applicable

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

MPC III L.P. (f/k/a Matrix Partners China III, L.P.)

Signature:	/s/ David Su
Name/Title:	David Su, Director of the general partner of the Reporting Person's general partner
Date:	08/14/2025

MPC III-A L.P. (f/k/a Matrix Partners China III-A, L.P.)

Signature:	/s/ David Su
Name/Title:	David Su, Director of the general partner of the Reporting Person's general partner
Date:	08/14/2025

MPC Management III L.P. (f/k/a Matrix China Management III, L.P.)

Signature:	/s/ David Su
Name/Title:	David Su, Director of the Reporting Person's general partner
Date:	08/14/2025

MPC GPGP III Ltd. (f/k/a Matrix China III GP GP Ltd.)

Signature:	/s/ David Su
Name/Title:	David Su, Director
Date:	08/14/2025

MPC III HK Limited (f/k/a Matrix Partners China III Hong Kong Limited)

Signature:	/s/ David Su
Name/Title:	David Su, Director
Date:	08/14/2025

David Su Tuong Sing

Signature:	/s/ David Su
Name/Title:	David Su
Date:	08/14/2025