Atom Investment, L.P., a Cayman Islands limited partnership formed in August 2020, has cut its stake in Rigaku Holdings Corporation, listed on the Tokyo Stock Exchange's Prime Market under ticker 268A, to almost nothing. A fifth amended large shareholding report filed with the Kanto Local Finance Bureau on August 13, 2026 shows the fund's holding fell from 27.28% to 0.29% of Rigaku's 226,516,100 outstanding shares.
Atom Investment's general partner is Atom Investment GP, L.L.C., represented by vice president Susan Bass. The filing was submitted through counsel at a Tokyo law firm.
The bulk of the reduction traces to a single transaction. Atom Investment signed a share transfer agreement with Onto Innovation Inc. on April 21, 2026, agreeing to hand over 61,123,436 ordinary shares, 26.98% of Rigaku. The deal settled on August 12, 2026, at ¥1,850 per share.
| Date | Buyer | Shares | % of Shares Outstanding | Price per Share |
|---|---|---|---|---|
| June 25, 2026 | Nomura Securities | 3,786,400 | 1.67% | ¥2,623.88 |
| August 12, 2026 | Onto Innovation Inc. | 61,123,436 | 26.98% | ¥1,850 |
That price sits well below what Atom Investment collected in an earlier, smaller disposal. On June 25, 2026, the fund sold 3,786,400 shares, 1.67% of Rigaku, off-market to Nomura Securities at ¥2,623.88 per share. The filing does not explain the gap between the two prices.
What is left of the position: 650,664 shares, or 0.29% of Rigaku. Atom Investment reports its holding purpose as pure investment and lists no material proposal actions attached to the stake. The stated reason for filing is a decrease of one percentage point or more in its shareholding ratio, the trigger for a short-term large transfer disclosure under Japan's large shareholding rules.
Atom Investment remains bound by a lock-up it signed on June 1, 2026 with four joint global coordinators: Morgan Stanley & Co. International plc, Nomura Securities, BofA Securities and JPMorgan Securities. That agreement bars further sales of Rigaku shares through September 5, 2026, with carve-outs covering underwritten offerings, greenshoe-related sales and the transfer to Onto Innovation itself.