Kek. So contrived.
Why did he even pretend to forget his at all?
But still, I find it odd that they'd be willing to go under his umbrella in the first place.
What if it isn't actually magic at all, and is just a totally ordinary (tiny) umbrella? And here he is trying to get his raep on with girls that were actually already interested in him.
That said, what guy would ever even want to use such a tiny umbrella, let alone try to share one? Frankly the bigger one with flowers is LESS girly than that tiny, dainty thing he is holding.
He should just claim the flower umbrella, give the girls the other one, and let them get their yuri on.