Yuuryou Kenkou Seito Shinsakai no Kiroku

Synopsis

In a world where physical education is done nude like the Olympics of old, boys and girls don't usually exercise together. Tada attends school with his childhood friend Aya when a sudden unexpected rainstorm forces the boys indoors where they share PE with the girls.

Today, Tada is especially lucky because it's physical fitness exams and the professors ask Tada to help take measurements and participate in the exams.