He's a Cute-faced Monster 卍: I'm a Former School Gang Leader, But This Kid Wants My Body

When he was in high school, Eiji was the legendary leader of the school gang at Ara High School, only for delinquents. Now he works as a carpenter and lives a peaceful life. But then, his younger brother gets into some trouble and Eiji ends up helping him. He meets the present gang leader at Ara High, Rui, who falls in love with him at first sight. Now Rui is relentlessly pursuing him...!! An aggressive sweet-faced rebel and a straight, tough former gang leader. A battle to protect his pride and chastity begins!

(Source: Renta!)

Note: Includes one extra chapter.