>>282960670
It was a total spur of the moment decision for Momo to go to Moe's house and drag Ichi along, he was so caught up in the flow that he didn't even think to give Yamada a heads up that he was going there until he was already there. Would probably have been fine if she wanted to show up, though.

>but it is okay for her to meet her boyfriend in public on Christmas?

Meeting up on Christmas wasn't planned, and he also immediately took her to a place where nobody was around.