It's actually not that sudden... If you look at it from his perspective he's just pursuing someone who he understands he didn't know her before so it's not sudden. He just has a quirky little personality. I kind of don't mind who she dates but it feels like he would be the best.
it is sudden tho in term of storytelling, this guy was suddenly introduced 50ch in and then straight to make a move on her. she has a better chemistry with the red hair even tho i would like them to be just friends. and also usually this kind of progression only done for someone with ulterior motives.
The romance w the GM kinda makes me turn off, like out of nowhere??? So sudden??? It would be nice if it was that red hair or orange hair guy is the male lead yknow, they have kinda good chemistry and cute but it would be good if the story focus more on her personal growth rather than bombing romance into the story.