Kimi no Koto ga Suki de Ienai.

It's been thirty years since meteorites from space turned everyone on the Earth gay. In a world where heterosexuality no longer exists, Kazusa Takanashi falls for her childhood friend Ayumu–a boy. Though she's doing everything she can to act normal whenever they hang out, her love for Ayumu is growing stronger by the day. How much longer can she hide her secret feelings?

(Source: Seven Seas Entertainment)