Doesn't she supposedly have a boyfriend?
Come to think of it, she was going on about double dates when talking to the other girl, but was talking about just the three of them meeting again when in front of MC. Quite a weird discrepancy. So he probably doesn't know she has a boyfriend. Still, it's probably safe to assume it, and in this situation it is completely normal to ask her about it and use it as reason to turn her down.
It seems no one in this work is gonna act rational, I should lower my expectations.
