Details of how many shares it will acquire and how much it will pay per share will be subject to negotiations, Aeon said.

Oasis and Aeon each have about a 13% holding in Tsuruha.

An increase in Aeon's stake would add to its drugstore business, a key growth driver for the firm, which in the same sector holds 51% of Welcia Holdings and 10% of Kusuri No Aoki Holdings.

An Aeon spokesperson said it had notified Tsuruha about its talks with Oasis for a possible stock purchase. The talks are being held without approval from Tsuruha, although that is not required for an acquisition to proceed, the spokesperson added.

Tsuruha declined to comment. Oasis could not immediately be reached for comment.

(Reporting by Kiyoshi Takenaka, Makiko Yamazaki and Ritsuko Shimizu; Editing by Jamie Freed and Jan Harvey)