The school has a tradition where couples exchange something like a wristband(?) for whatever reason during the school festival. The main couple does this, of course, and the male lead ends up in the infirmary at some point. The female lead somehow loses the guy's wristband and another girl takes it, bringing it to the infirmary to show the ML. She tells him that the FL threw it away, so she took it. ML doesn't believe her and tells her there's no way FL would do it.

That's the only part I remember from the manga and I have no idea what any of them look like. I really wanna find it again 😔