Blue Flag Vol. 1 (manga)

An unexpected love quadrangle with a dash of unrequited love as two classmates, a boy and a girl, begin to fall for each other when each of their best friends have already fallen for them.

It's the last year of high school, and love is in the air. Romantic feelings that have been building up over years of friendship come to light. When Taichi's classmate Futaba asks him to help her confess to his best friend, Toma, it sparks the catalyst that begins the sweet and heart-wrenching journey of their third and final year of high school.

For some reason, Taichi Ichinose just can't stand Futaba Kuze. But at the start of his third year in high school, he finds himself in the same homeroom as her, along with his childhood friend Toma Mita, a star athlete. But one day, Futaba opens up to Taichi and admits she has a crush on Toma. She then asks for his help in confessing to him! There's just one problem--Toma seems to already have a secret crush on someone else.