FL thinks the ML cheated on him

I don't remember, but I think it was a Taiwanese drama, but it could probably be something else. Either way, the drama basically starts with the FL going to the ML's apartment to surprise him or whatever, and she thinks she sees him in bed with another girl, but in fact it's the ML's best friend or brother and some girl, and then she disappears a few years before coming back, still thinking the ML has cheated on her.