Kakureta Tora ni Ryuu Monzetsuchuu

Tatsuya, a very popular idol, takes a bet from Usagi of the same group and promises to drop their manager, No. 25 (a guy), and go out with him...if they lose. He was only confident of winning, but the result was defeat. He is the worst type of person for Tatsuya: sloppy, tacky, and unrewarding despite his best efforts. And most problematic of all, Tatsuya was a womanizer and had no experience with men at all.