Kusattemo, Hatsukoi.

Fujiyoshi Murasaki, a first-year high school girl, transfers to an all-boys school, hiding her gender. The reason for transferring is to be able to keep a closer eye on two handsome guys who are her "favorite couple" that she saw on the train one day. In order to enjoy her fujoshi life for the fullest during her three years of high school, Murasaki approaches them in an attempt to become friends with them. (Source: Natalie, translated)