Seven & I Holdings is embarking on its biggest-ever overhaul, betting that a bold breakup will help fend off an unsolicited takeover proposal from a smaller rival and make up for a sluggish profit outlook.

"We are going to speed up our transformation,” CEO Ryuichi Isaka said in his first remarks since a buyout approach from Canada’s Alimentation Couche-Tard became public in August.

Seeking to restore profitability and focus more on convenience stores, Isaka laid out a major revamp: "This plan is designed to bring out our strengths and achieve greater growth.”