I don't remember much of this series but Osamu... You're done bro
Objectively, Osamu didn't do anything wrong (yet). He had a reservation, his career focused girlfriend ditched him (again), he met a friend to go ahead and use it.
Of course we know that objective don't mean shit and that ain't gonna fly.
Honestly the RIGHT move when your partner says they are stuck at work for 3 hours was to go get some takeway plus a cake, take it to their work, and see if they can take a break. (If you want to be a real chad, get some LED candles and a tablecloth) if they can't just leave them the bag.
But not just for RomCom reasons, that relationship is honestly done.