Miyoshi is failing a class and his teacher offers him some extra credit

Either Miyoshi or your character wants to practice kissing so they don't look lame when they finally get to kiss a future significant other. It gets more heated. For this one I do have a slight preference that it's someone around Miyoshi's age range (like in the 15-18 range) but I don't an older partner.

Miyoshi is a bit of a normie boy. I’d like to make him not normie. Maybe some shady gender bender pills he found an ad for online, or a potion that turns one into a cute monster person, or a vampire transformation situation, or some vague medical trial. I’m not picky. Your character can join in on the fun too.

Miyoshi canonically loves little useless gadgets and gizmos.
So it would make sense if he signed up for say a monthly random gadget subscription box.
It would be hilarious if by accident he got a box full of sex toys instead of fun useless little gizmos. It would be even more hilarious if his friend was visiting him when he opens it.