TOKYO - Japan's Seven & i Holdings must act fast to negotiate a takeover bid from Canada's Alimentation Couche-Tard that has "historic implications", said a fund manager at shareholder Artisan Partners Asset Management.

Couche-Tard, owner of Circle-K convenience stores, last week said it had approached Seven & i about a possible acquisition. It did not disclose a potential deal value, but a deal would likely be the biggest-ever overseas buyout of a Japanese firm.

Artisan has been a critic of Seven & i's management and structure since 2019. It said it is an active - not activist - shareholder which engages with corporate management and boards.

Fund manager Ben Herrick said Seven & i's board should negotiate with Couche-Tard while the offer remains friendly to increase the chances of a positive outcome for stakeholders.

Herrick declined comment on whether his fund has been in contact with Seven & i management. Seven & i, which operates the global 7-Eleven convenience store chain, said it does not comment on individual shareholders.

"The most important part of this deal, for both the reputation of the board and for corporate Japan, is that shareholders receive a fair, independently managed process," Herrick, associate portfolio manager of Artisan's International Value team, said in an emailed response to questions from Reuters.

"The outcome of this process has potentially historic implications," Herrick said.

U.S.-based Artisan holds 0.85% of Seven & i's outstanding shares, LSEG data showed. Bloomberg News earlier reported on the fund's views on the bid.

Artisan, as well as activist investors Third Point and ValueAct Capital, have criticised Seven & i for low returns and questioned its corporate governance.

Herrick said Artisan's efforts helped bring about an independent board and chairman at Seven & i that can hold management accountable and "realise the value of this world-class asset".

"We did not arrive at this juncture because corporate oversight and capital allocation were best in class," he said.

(Reporting by Rocky Swift; Editing by Miral Fahmy and Christopher Cushing)