Bain Capital and LY Corp. have submitted a joint offer to acquire Tokyo-listed Kakaku.com Inc., the $3.7 billion price comparison site operator fielding a takeover by EQT AB.

US private equity fund Bain and SoftBank Corp.-affiliate LY have offered to buy all of Kakaku’s shares, launching a bidding war, people familiar with the matter said. LY, which operates one of Japan’s largest search engines Yahoo Japan, seeks synergies with Kakaku’s Japanese price comparison services and restaurant search portal Tabelog, the people said, asking not to be named as the talks are private.