The Moment We Start Living Together, I Get Eaten.

Overview

Aihara, a straitlaced office worker who plays in a concert band on the side, is having a hard time moving on from his first love. But one day, Hayama, the very classmate who’d first stolen Aihara’s heart in high school, joins the band. Reunited with an old flame, Aihara’s feelings are sure to be rekindled, especially when they share a passionate kiss. After Hayama pins him to the ground, Aihara won’t be able to resist the aches of his heart—and his body! Two men share a sweet refrain from their youth in this dramatic reunion romance! (Source: Seven Seas Entertainment) Note: Includes the one-shot "Koiwazurai wa Shigoto no Ato de (恋わずらいは仕事のあとで, Leave the Lovesickness for When the Work Day's Done)", and an extra chapter.

Source: AniList