One summer day... In Rei's class, only the poor students were gathered together for summer classes. The temperature in the classroom rose rapidly due to the relentless sunlight, and Rei felt uncomfortable in her sweaty pants. That night, Rei picked up her husband's loincloth. "This one seems to have good ventilation..." And from the next day, Rei put on the loincloth and went to work, but... However, Rei felt strange with her lower body that was different from usual. She was unaware that the students had noticed her strange behavior...