the adult alumni, ntr, who was at his first drinking party when he was 20 years old... this is kasuse.

Kamejiro, who is in love with Kokoro, learns that she was invited to alumni party during her school days. Kamejiro, who has just turned 20 and is worried about getting him to go to a drinking place even though he hasn’t been used to alcohol yet, contacted many times during the alumni meeting. The next day, when I returned home in the morning, I stopped by and said nothing. Kamejiro became even more worried, but he witnessed a man (formerly Kare) who met again at his home at alumni's meeting, and saw part of the scene of an affair, so he started to jealousy.