@Battousai124: Not much to translate. Youmu has a boyfriend and comes to realize that he's sort of using her more for sexual favors and has never told her he loves her, so she decides that her goal is to "win his heart and his lower half". So she decides to get more into it and taking the initiative with sex (and now knowing what he's into thanks to the doujinshi/erohon she found under his bed). Hence her going all out, and succeeding since on the last page the guy tells Youmu that he loves her and asks her to marry him.