Oasis could make "important proposals" to the company to protect shareholder values, it said in a regulatory filing on Wednesday.

The filing follows news last month that Oasis plans to sell its 13% stake in Tsuruha Holdings to Japanese retail giant Aeon Co which plans to merge the drugstore chain with another.

Seven & I Holdings owns 7.83% of Ain's outstanding shares, making it the third-biggest shareholder, according to the company's website.

The Hong Kong-based fund is active in Japan and last month said it was opposed to Taisho Pharmaceutical's $5 billion management buyout as it believes the acquisition price was too low.

(Reporting by Mariko Katsumura; Editing by Edwina Gibbs)