From Ai's Bookshelf:
Akira Tsubakiya has spent her whole life being told she looks like a boy. She’s super tall, she has a flat chest, and she’s not girly at all… In middle school, she made a promise with a boy who went to her cram school, Haru— a promise that they both would aim to get into the same high school, a prestigious academy. Haru told Akira that he likes girls with long hair, and since she started to fall for him, she grew it out. Now she’s graduating from middle school, and has decided to confess her feelings to Haru. Unfortunately, she finds out that he has a girlfriend—a super-cute, girly, long-haired girlfriend! Akira runs home and chops off all her hair, deciding that there’s no point to trying to be girly.
Fast forward to Akira’s first year in high school. She still wears a skirt, but she wears the top half of the guys’ uniform to school. She’s called “Prince Akira”, and all the girls are infatuated with her. Akira hasn’t seen Haru in a while, but she does bump into Haru’s “girlfriend”… who she discovers to be in fact a boy!