Who has been buying Tosei Corporation stock?

8 distinct investors have filed 8 disclosed large-shareholding filings in Tosei Corporation (8923), most recently on 2026-04-06. 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 Tosei Corporation have?

Tosei Corporation has 8 buy-side and 11 sell-side disclosures on record, covering ¥27.2B ($175.7M) in total reported value, spanning 2021-03-24 to 2026-04-06.

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.

Tosei Corporation 8923

Company

トーセイ株式会社Tosei Corporation

Investors

Buys

Total Value

¥27.2B ($175.7M)

Avg Return

+60.85%

Last Filing

2026-04-06

Tosei Corporation (8923) has 8 disclosed large-shareholding filings and 11 disclosed disposals on record, filed by 8 distinct investors. Together those filings cover ¥27.2B ($175.7M) in reported transaction value. The earliest filing StockDrifts holds for Tosei Corporation is dated 2021-03-24; the most recent is 2026-04-06. Across these filings the average return since disclosure is +60.85%, 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
2026-07-13	BUY	Market Buy	ダルトン・インベストメンツ・インク(Dalton Investments, Inc.) Dalton Investments, Inc.	activist	5.9M	¥1,733	-0.5%	¥1.8B ($11.6M)
2026-04-06	BUY	Market Buy	グランサム、マヨ、ヴァンオッテルローアンドカンパニーエルエルシー(Grantham, Mayo, Van Otterloo & Co. LLC) Grantham, Mayo, Van Otterloo & Co. LLC	activist	4.9M	¥1,662	+3.7%	¥8.2B ($53.0M)
2025-06-05	BUY	negotiated	ダルトン・インベストメンツ・インク(Dalton Investments, Inc.) Dalton Investments, Inc.	activist	2.4M	¥1,233.5	+39.8%	¥3.0B ($19.4M)
2025-02-12	BUY	Market Buy	山口誠一郎 Seiichiro Yamaguchi	activist	5.4M	¥1,212.5	+42.2%	¥24M ($152K)
2025-02-12	BUY	Market Buy	有限会社ゼウス・キャピタル Zeus Capital Ltd.	strategic	6.0M	¥1,212.5	-	-
2025-02-12	BUY	Market Buy	合同会社センフル Senful LLC	strategic	515.0K	¥1,212.5	-	¥624M ($4.0M)
2024-11-19	SELL	negotiated	ダルトン・インベストメンツ・インク(Dalton Investments, Inc.) Dalton Investments, Inc.	activist	1.8M	¥1,190.5	-44.8%	¥753M ($4.9M)
2024-06-06	BUY	negotiated	山口誠一郎 Seiichiro Yamaguchi	activist	5.4M	¥1,163.5	+48.2%	¥6.1B ($39.5M)
2024-06-06	BUY	negotiated	有限会社ゼウス・キャピタル Zeus Capital Ltd.	strategic	6.0M	¥1,163.5	-	-
2024-06-03	BUY	negotiated	ダルトン・インベストメンツ・インク(Dalton Investments, Inc.) Dalton Investments, Inc.	activist	2.4M	¥1,128.5	+52.8%	¥2.8B ($17.8M)
2024-05-30	SELL	negotiated	山口誠一郎 Seiichiro Yamaguchi	activist	12.9M	¥1,096	-57.3%	¥123M ($792K)
2024-05-30	SELL	negotiated	有限会社ゼウス・キャピタル Zeus Capital Ltd.	strategic	6.0M	¥1,096	-57.3%	¥59M ($379K)
2024-05-29	BUY	acquisition	名古屋鉄道株式会社 Nagoya Railroad Co., Ltd.	strategic	7.5M	¥1,083	+59.2%	¥8.1B ($52.4M)
2024-04-02	SELL	Market Buy	グランサム、マヨ、ヴァンオッテルローアンドカンパニーエルエルシー(Grantham, Mayo, Van Otterloo & Co. LLC) Grantham, Mayo, Van Otterloo & Co. LLC	activist	2.0M	¥1,204	-43.2%	¥598M ($3.9M)
2023-04-21	BUY	Market Buy	グランサム、マヨ、ヴァンオッテルローアンドカンパニーエルエルシー(Grantham, Mayo, Van Otterloo & Co. LLC) Grantham, Mayo, Van Otterloo & Co. LLC	activist	2.5M	¥758	+127.4%	¥1.9B ($12.0M)
2023-02-17	BUY	Market Buy	スパークス・アセット・マネジメント株式会社 SPARX Asset Management Co., Ltd.	passive	2.4M	¥717.5	+140.3%	¥1.8B ($11.3M)
2022-08-24	SELL	Market Buy	グランサム、マヨ、ヴァンオッテルローアンドカンパニーエルエルシー(Grantham, Mayo, Van Ottterloo & Co. LLC) Grantham, Mayo, Van Ottterloo & Co. LLC	activist	2.1M	¥673.5	-156.0%	¥334M ($2.2M)
2021-08-24	SELL	Market Buy	グランサム、マヨ、ヴァンオッテルローアンドカンパニーエルエルシー(Grantham, Mayo, Van Ottterloo & Co. LLC) Grantham, Mayo, Van Ottterloo & Co. LLC	activist	2.6M	¥582.5	-196.0%	¥298M ($1.9M)
2021-05-26	SELL	Market Buy	サマランユーシッツ(SAMARANG UCITS) SAMARANG UCITS	passive	2.0M	¥525	-228.4%	¥304M ($2.0M)
2021-03-24	SELL	negotiated	山口誠一郎 Seiichiro Yamaguchi	activist	12.9M	¥474.403	-263.4%	¥46M ($298K)
2021-03-24	SELL	negotiated	山口誠一郎 Seiichiro Yamaguchi	activist	12.9M	¥474.403	-263.4%	¥46M ($298K)
2021-03-24	SELL	negotiated	有限会社ゼウス・キャピタル Zeus Capital Ltd.	strategic	6.0M	¥474.403	-263.4%	¥25M ($164K)
2021-03-24	SELL	negotiated	有限会社ゼウス・キャピタル Zeus Capital Ltd.	strategic	6.0M	¥474.403	-263.4%	¥25M ($164K)

Frequently asked questions

Who has been buying Tosei Corporation stock?: 8 distinct investors have filed 8 disclosed large-shareholding filings in Tosei Corporation (8923), most recently on 2026-04-06. 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 Tosei Corporation have?: Tosei Corporation has 8 buy-side and 11 sell-side disclosures on record, covering ¥27.2B ($175.7M) in total reported value, spanning 2021-03-24 to 2026-04-06.
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.