IDK what's up with y'all like, we got one whole flashback chapter like 1 volume in about anything substantial to Mai's character and like, a few panels of her POV here and there. It was like obvious Asumi was getting more swept up in casual lesbian sex than "reunion with destined romantic partner". We only get like, Mai was attracted (romantically) to Asumi when they were young, and Asumi didn't really understand the romantic implications of what they got up to together. Whereas the bulk of the manga has been, wow sex with new people in new ways is cool and fun. Now, the "new way", is someone who is romantically into her which is somewhat reciprocal. She's barrelling into, either oh, "I like this way the most, lets start multiple romances (wouldn't be out of the picture for her OR nanao really)" Or "oh this was really damn meaningful and I should be a bit more deliberate with this, lets pump the brakes on Mai/Nanao and figure out how I feel". Though really, she hasn't actually engaged much with what she's felt romantically for Mai, but has done much more per Nanao. To me it makes way more sense that someone besides Mai was going to spur some sort of development of her understanding her romantic desires, because they were really abstracted in the beginning, with the whole, "I'm going to find my Important Childhood Friend", since she's y'know, out of the picture.