Non-trading investments (Tables)

6 Months Ended

Sep. 30, 2025

Investments, Debt and Equity Securities [Abstract]

Summary of AFS debt securities

The following table presents the amortized cost and fair value of major types of AFS debt securities as well as cumulative unrealized gains and unrealized losses recognized through Accumulated other comprehensive income (loss) since acquisition as of March 31, 2025 and September 30, 2025.

	Millions of yen
	March 31, 2025
	Amortized cost(1)		Unrealized gains		Unrealized losses			Fair value
Japanese government securities	¥	25,001	¥	—	¥	(187	)	¥	24,814
Japanese agency and municipal securities		81,913		19		(1,495	)		80,437
Bank and corporate debt securities		1,790		—		(11	)		1,779
Total	¥	108,704	¥	19	¥	(1,693	)	¥	107,030
	Millions of yen
	September 30, 2025
	Amortized cost(1)		Unrealized gains		Unrealized losses			Fair value
Japanese government securities	¥	65,008	¥	—	¥	(248	)	¥	64,760
Japanese agency and municipal securities		120,963		—		(1,814	)		119,149
Bank and corporate debt securities		9,668		—		(69	)		9,599
Total	¥	195,639	¥	—	¥	(2,131	)	¥	193,508

(1) No allowances for credit losses have been recognized as of March 31, 2025 and September 30, 2025.

Summary of AFS debt securities categorized by contractual maturity

The following table presents the amortized cost and fair value of AFS debt securities, categorized by contractual maturity as of March 31, 2025 and September 30, 2025.

	Millions of yen
	March 31, 2025				September 30, 2025
	Amortized cost(1)		Fair value		Amortized cost(1)		Fair value
Japanese government securities
less than 1 year	¥	—	¥	—	¥	10,001	¥	9,977
1 year to 5 years		25,001		24,814		55,007		54,783
Subtotal	¥	25,001	¥	24,814	¥	65,008	¥	64,760
Japanese agency and municipal securities
1 year to 5 years	¥	81,913	¥	80,437	¥	120,963	¥	119,149
Subtotal	¥	81,913	¥	80,437	¥	120,963	¥	119,149
Bank and corporate debt securities
1 year to 5 years	¥	1,790	¥	1,779	¥	9,668	¥	9,599
Subtotal	¥	1,790	¥	1,779	¥	9,668	¥	9,599
Total	¥	108,704	¥	107,030	¥	195,639	¥	193,508

(1) No allowances for credit losses have been recognized as of March 31, 2025 and September 30, 2025 .

Summary of AFS debt securities in an unrealized loss position

The following table presents the fair value of major types of AFS debt securities that are in an unrealized loss position as of March 31, 2025 and September 30, 2025, and the duration of the unrealized loss status. An unrealized loss exists where the fair value of an individual AFS debt security is less than its amortized cost basis.

	Millions of yen
	March 31, 2025							September 30, 2025
	Fair value		Unrealized losses			Number of debt securities		Fair value		Unrealized losses			Number of debt securities
Japanese government securities
Less than 12 months	¥	24,814	¥	(187	)		4	¥	59,864	¥	(138	)		7
12 months or longer		—		—			—		4,896		(110	)		1
Subtotal	¥	24,814	¥	(187	)		4	¥	64,760	¥	(248	)		8
Japanese agency and municipal securities
Less than 12 months	¥	68,063	¥	(1,495	)		72	¥	108,024	¥	(1,546	)		103
12 months or longer		—		—			—		11,125		(268	)		15
Subtotal	¥	68,063	¥	(1,495	)		72	¥	119,149	¥	(1,814	)		118
Bank and corporate debt securities
Less than 12 months	¥	1,779	¥	(11	)		3	¥	9,599	¥	(69	)		17
Subtotal	¥	1,779	¥	(11	)		3	¥	9,599	¥	(69	)		17
Total	¥	94,656	¥	(1,693	)		79	¥	193,508	¥	(2,131	)		143