Who has been buying Mamiya-OP Co., Ltd. stock?

5 distinct investors have filed 14 disclosed large-shareholding filings in Mamiya-OP Co., Ltd. (7991), most recently on 2026-01-27. Each filer, their role, the number of shares and the price at filing are listed in the table on this page.

How many insider filings does Mamiya-OP Co., Ltd. have?

Mamiya-OP Co., Ltd. has 14 buy-side and 7 sell-side disclosures on record, covering ¥8.5B ($55.0M) in total reported value, spanning 2021-06-29 to 2026-01-27.

Do insider buys in Japanese stocks predict returns?

Not uniformly. StockDrifts scored 101,000+ Japanese large-shareholding filings on fixed 12-month forward returns and found the predictive power concentrated in specific filer types and filing patterns rather than spread evenly across all disclosures.

Mamiya-OP Co., Ltd. 7991

Company

マミヤ・オーピー株式会社Mamiya-OP Co., Ltd.

Investors

Buys

Total Value

¥8.5B ($55.0M)

Avg Return

-13.85%

Last Filing

2026-01-27

Mamiya-OP Co., Ltd. (7991) has 14 disclosed large-shareholding filings and 7 disclosed disposals on record, filed by 5 distinct investors. Together those filings cover ¥8.5B ($55.0M) in reported transaction value. The earliest filing StockDrifts holds for Mamiya-OP Co., Ltd. is dated 2021-06-29; the most recent is 2026-01-27. Across these filings the average return since disclosure is -13.85%, measured from each filing date to the latest available close.

Price & insider activity (12 months)

Recent filings

Date	Type	Source	Insider	Purpose	Shares	Price at filing	Return	Value
2026-01-27	SELL	Market Buy	株式会社データ・アート Data Art Co., Ltd.	activist	4.0M	¥1,704	+37.7%	¥833M ($5.4M)
2026-01-27	BUY	Market Buy	丹野裕介 Yusuke Tanno	activist	1.4M	¥1,704	-37.7%	¥23M ($150K)
2025-11-13	BUY	Market Buy	丹野裕介 Yusuke Tanno	activist	1.4M	¥1,701	-37.6%	¥198M ($1.3M)
2025-11-06	BUY	Market Buy	丹野裕介 Yusuke Tanno	activist	1.3M	¥1,702	-	¥199M ($1.3M)
2025-11-06	BUY	Market Buy	丹野裕介 Yusuke Tanno	activist	1.3M	¥1,702	-37.7%	¥199M ($1.3M)
2025-10-30	BUY	Market Buy	丹野裕介 Yusuke Tanno	activist	1.2M	¥1,912	-	¥328M ($2.1M)
2025-10-30	BUY	Market Buy	丹野裕介 Yusuke Tanno	activist	1.2M	¥1,912	-44.5%	¥328M ($2.1M)
2025-10-23	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	1.0M	¥1,922	-44.8%	¥230M ($1.5M)
2025-10-23	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	1.0M	¥1,922	-	¥230M ($1.5M)
2025-10-14	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	881.5K	¥1,707	-37.8%	¥185M ($1.2M)
2025-10-14	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	881.5K	¥1,707	-	¥185M ($1.2M)
2025-09-04	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	773.6K	¥1,898	-	¥1.5B ($9.5M)
2025-09-04	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	773.6K	¥1,898	-	¥395M ($2.5M)
2025-09-04	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	773.6K	¥1,898	-	¥395M ($2.5M)
2025-09-01	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	565.3K	¥1,888	-	¥1.1B ($6.9M)
2025-09-01	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	565.3K	¥1,888	-43.8%	¥1.1B ($6.9M)
2025-09-01	BUY	Market Buy	丹野裕介 Yusuke Tanno	passive	565.3K	¥1,888	-	¥1.1B ($6.9M)
2024-04-05	BUY	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	441.2K	¥1,525	-30.4%	¥638M ($4.1M)
2024-04-05	SELL	subscription	株式会社三井住友銀行 Sumitomo Mitsui Banking Corporation	other	10.9K	¥1,525	+30.4%	¥10M ($67K)
2024-03-25	BUY	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	631.7K	¥1,711	-38.0%	¥1.0B ($6.5M)
2024-03-25	BUY	subscription	株式会社三井住友銀行 Sumitomo Mitsui Banking Corporation	other	17.2K	¥1,711	-	-
2024-03-07	BUY	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	797.9K	¥1,671	-36.5%	¥1.2B ($7.9M)
2024-03-07	BUY	subscription	株式会社三井住友銀行 Sumitomo Mitsui Banking Corporation	other	17.2K	¥1,671	-	-
2024-02-21	BUY	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	954.1K	¥1,620	-34.5%	¥1.4B ($9.0M)
2024-02-21	SELL	subscription	株式会社三井住友銀行 Sumitomo Mitsui Banking Corporation	other	17.2K	¥1,620	+34.5%	¥11M ($68K)
2024-02-15	BUY	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	1.1M	¥1,580	-32.9%	¥1.5B ($9.9M)
2024-02-15	BUY	subscription	株式会社三井住友銀行 Sumitomo Mitsui Banking Corporation	other	23.5K	¥1,580	-	¥37M ($240K)
2024-02-07	SELL	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	1.3M	¥1,651	+35.7%	¥164M ($1.1M)
2024-02-05	SELL	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	1.4M	¥1,639	+35.3%	¥221M ($1.4M)
2024-01-29	SELL	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	1.5M	¥1,700	+37.6%	¥72M ($462K)
2024-01-24	SELL	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	1.6M	¥1,445	+26.6%	¥119M ($768K)
2024-01-10	BUY	subscription	SMBC日興証券株式会社 SMBC Nikko Securities Inc.	other	1.7M	¥1,343	-21.0%	¥2.3B ($15.0M)
2021-06-29	BUY	unknown	渡辺靖子 Yasuko Watanabe	strategic	265.0K	¥685	+54.9%	¥182M ($1.2M)

Frequently asked questions

Who has been buying Mamiya-OP Co., Ltd. stock?: 5 distinct investors have filed 14 disclosed large-shareholding filings in Mamiya-OP Co., Ltd. (7991), most recently on 2026-01-27. Each filer, their role, the number of shares and the price at filing are listed in the table on this page.
How many insider filings does Mamiya-OP Co., Ltd. have?: Mamiya-OP Co., Ltd. has 14 buy-side and 7 sell-side disclosures on record, covering ¥8.5B ($55.0M) in total reported value, spanning 2021-06-29 to 2026-01-27.
Do insider buys in Japanese stocks predict returns?: Not uniformly. StockDrifts scored 101,000+ Japanese large-shareholding filings on fixed 12-month forward returns and found the predictive power concentrated in specific filer types and filing patterns rather than spread evenly across all disclosures.

More on this data

Every trade listed above comes from an official regulatory disclosure. For how StockDrifts scores these disclosures, see the Japan insider signal tier research, or browse every Japanese stock we track.