Earnings per share (Details) - JPY (¥) ¥ / shares in Units, ¥ in Millions	3 Months Ended	9 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024
Earnings per share [abstract]
Net profits (losses) for the period attributable to owners of Coincheck Parent	¥ 405	¥ (15,445)	¥ (617)	¥ (14,992)
Net profits (losses) for the period attributable to owners of Coincheck Parent	¥ 405	¥ (15,445)	¥ (617)	¥ (14,992)
Basic net earnings (losses) per share (in Yen per share)	¥ 3.00	¥ (124.32)	¥ (4.66)	¥ (121.76)
Diluted net earnings (losses) per share (in Yen per share)	¥ 2.91	¥ (124.32)	¥ (4.66)	¥ (121.76)
Weighted-average number of shares, basic (in shares)	135,165,111	124,229,646	132,272,670	123,130,979
Weighted-average number of shares, diluted (in shares)	139,028,575	124,229,646	132,272,670	123,130,979

The weighted average number of ordinary shares outstanding plus the weighted average number of ordinary shares that would be issued on the conversion of all the dilutive potential ordinary shares into ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator), divided by the weighted average number of ordinary shares outstanding during the period (the denominator), both adjusted for the effects of all dilutive potential ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The profit (loss) attributable to ordinary equity holders of the parent entity. [Refer: Profit (loss)]

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The profit (loss) attributable to ordinary equity holders of the parent entity, adjusted for the effects of all dilutive potential ordinary shares. [Refer: Profit (loss)]

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The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor.

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