Don't Toy with Me, Miss Nagatoro 15 (manga)

Now that Senpai has finally realized his feelings for Nagatoro, he’s left with one big problem: a dire lack of confidence that is spilling over into his paintings and endangering his dreams of getting into an arts university. At a loss for how to help, Nagatoro turns for aid to the former club president, who is only too happy to oblige. But when the president’s solution turns out to require quite a bit more exposure than anybody anticipated, Nagatoro must decide just how much skin she’s willing to put in the game.