Taiyou yori mo Mabushii Hoshi

Sae and Koki have been friends since childhood. One fateful day at the end of middle school, she has a revelation: Koki has grown up! Now they're in high school, and she has another revelation: she has feelings for Koki! But Sae isn't the only girl who does... The question is, who does Koki have feelings for?!

(Source: VIZ Media)