Mild

Shingo Takahashi, who had an ordinary but happy family with his wife and daughter, suddenly finds himself burdened with a 40 million yen debt because he co-signed a loan for a friend who disappeared... He's even told he might have to use his wife and daughter's bodies to repay it. Cornered, Shingo is offered a job in the underworld if he can't come up with the money to repay the debt!? A suspenseful thriller about a ruthless job in the underworld!

(Source: Shonen Gahosha, translated)