Who has been buying Tsubota Laboratory Incorporated stock?

3 distinct investors have filed 4 disclosed large-shareholding filings in Tsubota Laboratory Incorporated (4890), most recently on 2025-08-29. 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 Tsubota Laboratory Incorporated have?

Tsubota Laboratory Incorporated has 4 buy-side and 16 sell-side disclosures on record, covering ¥3.8B ($24.4M) in total reported value, spanning 2022-06-13 to 2025-08-29.

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.

Tsubota Laboratory Incorporated 4890

Company

株式会社坪田ラボTsubota Laboratory Incorporated

Investors

Buys

Total Value

¥3.8B ($24.4M)

Avg Return

-57.19%

Last Filing

2025-08-29

Tsubota Laboratory Incorporated (4890) has 4 disclosed large-shareholding filings and 16 disclosed disposals on record, filed by 3 distinct investors. Together those filings cover ¥3.8B ($24.4M) in reported transaction value. The earliest filing StockDrifts holds for Tsubota Laboratory Incorporated is dated 2022-06-13; the most recent is 2025-08-29. Across these filings the average return since disclosure is -57.19%, 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
2026-06-19	BUY	private	キャンターフィッツジェラルドヨーロッパ(Cantor Fitzgerald Europe) Cantor Fitzgerald Europe	passive	5.9M	¥219	+17.4%	¥1.3B ($8.3M)
2025-08-29	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	12.2M	¥366	+29.8%	¥107M ($688K)
2025-08-29	SELL	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥366	+29.8%	¥9M ($61K)
2025-08-28	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	12.2M	¥367	+30.0%	¥128M ($825K)
2025-08-28	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	12.2M	¥367	+30.0%	¥107M ($690K)
2025-08-28	SELL	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥367	+30.0%	¥9M ($61K)
2025-08-28	SELL	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥367	+30.0%	¥9M ($61K)
2024-11-15	BUY	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥429	-	-
2024-11-15	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	12.4M	¥429	+40.1%	¥181M ($1.2M)
2024-11-15	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	12.4M	¥429	+40.1%	¥181M ($1.2M)
2024-11-15	SELL	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥429	+40.1%	¥1M ($7K)
2024-10-07	SELL	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥470	+45.3%	¥1M ($8K)
2024-10-07	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	12.9M	¥470	+45.3%	¥95M ($613K)
2023-08-18	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	13.1M	¥492	+47.8%	¥151M ($973K)
2023-08-18	SELL	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥492	+47.8%	¥16M ($105K)
2023-01-24	SELL	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥895	+71.3%	¥18M ($117K)
2023-01-24	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	13.2M	¥895	+71.3%	¥72M ($467K)
2022-07-22	SELL	negotiated	坪田一男 Kazuo Tsubota	activist	13.2M	¥1,210	+78.8%	¥690M ($4.5M)
2022-07-22	BUY	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥1,210	-	-
2022-06-28	BUY	negotiated	坪田一男 Kazuo Tsubota	activist	13.8M	¥738	-65.2%	¥10.2B ($65.8M)
2022-06-28	BUY	negotiated	株式会社坪田 Tsubota Co., Ltd.	activist	3.2M	¥738	-65.2%	¥2.4B ($15.2M)
2022-06-27	BUY	Market Buy	大髙功 Isao Otaka	passive	1.8M	¥722	-	¥62M ($398K)
2022-06-27	BUY	Market Buy	大髙功 Isao Otaka	passive	1.8M	¥722	-	¥62M ($398K)
2022-06-24	BUY	Market Buy	大髙功 Isao Otaka	passive	1.8M	¥775	-66.8%	¥1.4B ($9.2M)
2022-06-13	BUY	acquisition	大髙功 Isao Otaka	passive	1.8M	-	-	-
2022-06-13	BUY	Market Buy	大髙功 Isao Otaka	passive	1.8M	-	-	-

Frequently asked questions

Who has been buying Tsubota Laboratory Incorporated stock?: 3 distinct investors have filed 4 disclosed large-shareholding filings in Tsubota Laboratory Incorporated (4890), most recently on 2025-08-29. 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 Tsubota Laboratory Incorporated have?: Tsubota Laboratory Incorporated has 4 buy-side and 16 sell-side disclosures on record, covering ¥3.8B ($24.4M) in total reported value, spanning 2022-06-13 to 2025-08-29.
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.