Nimanbun no Ichi no Amatsubutachi - One in 20,000 raindrops

Satoshi Kuga, who leads an isolated high school life with a cynical attitude, is dreading the school trip starting tomorrow. This is because he has been assigned to the same group as the popular clique in his class, who are enjoying their youth to the fullest. However, it seems there are hidden tensions within this seemingly close-knit group, and he gradually finds himself drawn into their problems.

[From Steam]