I had an idea for an episode that can be done during the day. So, in summary...
One day Joel receives a letter from his mother who says: "Hello, Joel. They have recently opened some luxury hot springs here in the city and have started distributing limited edition tickets with which you can bathe for free one time, My colleague got me a handful and I thought I'd give them to you. I tried these hot springs myself and they're fabulous, I highly recommend you try them with some of your friends! I love you, mom." Joel finds four tickets inside the envelope and thinks he wants to invite his friends to school to go to the hot springs together in the afternoon. However, if everyone found out about the tickets immediately, those who weren't invited would be upset and Joel decides to meet privately with whoever he wants to invite and give them the tickets, hiding the truth from the others. For Joel, the idea of being in the company of his friends in the middle of warm water and completely naked is relaxing, embarrassing and exciting at the same time and he doesn't want to give up the opportunity.
So, what do you think? If you want, you can change it, putting only two tickets for Joel and his partner, or eight tickets so that everyone comes.