Senpai could have made a formula to age her up. She did the exact opposite not too long ago, and how different can it be from the one that ages herself up? But that would be too easy, gotta make it convoluted with an even bigger age gap
The fighting was funny and cute, but also worries me it'll feed into stupid drama later on. I don't expect Saku to be more than a good friend, but then I didn't expect Botan to be more than the female lead's friend good either.
@sighoon he helped Katagiri avoid his peeping tom friends instead of taking an ideal opportunity to ogle Ooki, so maybe there's hope for him. I wish he'd actually try talking to the girls tho instead of creeping from a distance