Oni wa Warau ka

Ordinary high schooler Hoshitani witnesses the carefree Kashiwase having an affair with their P.E. teacher. Since then it's weighed on Hoshitani's mind, but one day on a field trip for P.E. he has an unexpected opportunity to get closer to Kashiwase, who teases him by asking him if he's on his period. In an absurd world where adults selfishly play around, two young men earnestly cuddle together.

(Source: Must be Endless)