Serina is also the girl in the second asmr chapter
Anyways they were kinda hinting at this a bit with her, so it's nice that we're getting her as an active persuer
Like it does feel that the author initially wanted Mai to be endgame but as the series got more and more popular and the other girls more fleshed out, that yeah, she has a lot of chemistry with the other girls and it would be a shame to not explore that. Like she is very different with Nanao and Serina in terms of intensity