Who has been buying Base Co., Ltd. stock?

9 distinct investors have filed 6 disclosed large-shareholding filings in Base Co., Ltd. (4481), most recently on 2025-12-18. 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 Base Co., Ltd. have?

Base Co., Ltd. has 6 buy-side and 14 sell-side disclosures on record, covering ¥42.2B ($272.0M) in total reported value, spanning 2021-12-23 to 2025-12-18.

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.

Base Co., Ltd. 4481

Company

ベース株式会社Base Co., Ltd.

Investors

Buys

Total Value

¥42.2B ($272.0M)

Avg Return

-10.34%

Last Filing

2025-12-18

Base Co., Ltd. (4481) has 6 disclosed large-shareholding filings and 14 disclosed disposals on record, filed by 9 distinct investors. Together those filings cover ¥42.2B ($272.0M) in reported transaction value. The earliest filing StockDrifts holds for Base Co., Ltd. is dated 2021-12-23; the most recent is 2025-12-18. Across these filings the average return since disclosure is -10.34%, 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
2025-12-18	SELL	unknown	中山克成	activist	23.1K	¥3,225	+0.5%	¥6M ($39K)
2025-12-18	SELL	unknown	中山秋子	activist	31.0K	¥3,225	+0.5%	¥6M ($39K)
2025-12-18	SELL	unknown	中山アセット株式会社	strategic	7.7M	¥3,225	+0.5%	¥649M ($4.2M)
2023-12-04	SELL	unknown	富士通株式会社 Fujitsu Limited	strategic	200.3K	¥3,445	+6.8%	¥4.9B ($31.3M)
2023-12-04	BUY	unknown	中山克成 Katsunari Nakayama	activist	23.1K	¥3,445	-	-
2023-12-04	BUY	unknown	中山アセット株式会社 Nakayama Asset Co., Ltd.	strategic	7.7M	¥3,445	-6.8%	¥26.4B ($170.1M)
2023-12-04	BUY	unknown	中山秋子 Akiko Nakayama	activist	31.0K	¥3,445	-	-
2023-05-09	SELL	unknown	三井住友トラスト・アセットマネジメント株式会社 Sumitomo Mitsui Trust Asset Management Co.,Ltd.	other	185.8K	¥6,140	+47.7%	¥67M ($432K)
2023-05-09	BUY	unknown	日興アセットマネジメント株式会社 Nikko Asset Management Co.,Ltd.	other	527.7K	¥6,140	-47.7%	¥3.2B ($20.6M)
2022-12-01	BUY	unknown	中山秋子 Akiko Nakayama	activist	31.0K	¥3,900	-17.7%	¥11.5B ($73.9M)
2022-12-01	SELL	unknown	中山アセット株式会社 Nakayama Asset Co., Ltd.	strategic	7.7M	¥3,900	+17.7%	¥177M ($1.1M)
2022-12-01	BUY	unknown	中山克成 Katsunari Nakayama	activist	23.2K	¥3,900	-17.7%	¥8.4B ($54.3M)
2022-08-25	SELL	unknown	中山克成 Katsunari Nakayama	activist	101.6K	¥3,175	-1.1%	¥3M ($19K)
2022-08-25	SELL	unknown	中山秋子 Akiko Nakayama	activist	75.5K	¥3,175	-1.1%	¥3M ($19K)
2022-08-25	SELL	unknown	中山アセット株式会社 Nakayama Asset Co., Ltd.	strategic	3.9M	¥3,175	-1.1%	¥130M ($836K)
2022-04-06	SELL	unknown	中山克成 Katsunari Nakayama	activist	101.6K	¥3,245	+1.1%	¥3M ($19K)
2022-04-06	SELL	unknown	中山秋子 Akiko Nakayama	activist	75.5K	¥3,245	+1.1%	¥3M ($19K)
2022-04-06	SELL	unknown	中山アセット株式会社 Nakayama Asset Co., Ltd.	strategic	3.9M	¥3,245	+1.1%	¥137M ($883K)
2022-04-06	BUY	unknown	三井住友トラスト・アセットマネジメント株式会社 Sumitomo Mitsui Trust Asset Management Co.,Ltd.	other	97.0K	¥3,245	-1.1%	¥315M ($2.0M)
2022-04-06	BUY	unknown	日興アセットマネジメント株式会社 Nikko Asset Management Co.,Ltd.	other	352.5K	¥3,245	-1.1%	¥1.1B ($7.4M)
2021-12-23	SELL	unknown	伊藤康子 Yasuko Ito	strategic	93.9K	¥2,002.5	-60.3%	¥58M ($371K)
2021-12-23	SELL	unknown	伊藤商事株式会社 Ito Corporation	strategic	683.1K	¥2,002.5	-60.3%	¥173M ($1.1M)
2021-12-23	BUY	unknown	伊藤依光 Yorimitsu Ito	strategic	30.0K	¥2,002.5	-	¥60M ($388K)

Frequently asked questions

Who has been buying Base Co., Ltd. stock?: 9 distinct investors have filed 6 disclosed large-shareholding filings in Base Co., Ltd. (4481), most recently on 2025-12-18. 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 Base Co., Ltd. have?: Base Co., Ltd. has 6 buy-side and 14 sell-side disclosures on record, covering ¥42.2B ($272.0M) in total reported value, spanning 2021-12-23 to 2025-12-18.
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.