In a way it's perfection how we don't see their first kiss on-screen even though all the perverted stuff that happened before.
The date itself had an excellent build up too, you could see the amazing mood too before Himeme ruined it, but because she interfered now Minori promised Koko for the rest of her life after one of the most serious kisses that I have seen in any manga, so good job I guess? The 2 alone girls can console each other, it's still Christmas.
It's kinda hilarious that a lot of manga just ends when the main couple gets together but this one of the few exceptions that keeps going and I'm grateful for it.