I'm confused...
When were they actually shown to be anything other than classmates?
Other than her introducing herself to him and stalking him, they made absolutely no contact whatsoever.
Background character development? I don't think it's that.
What about nonsensical forced relationships chained to both of the characters? That's probably it.
When the girl finally catches up to him and asks him if he's the masked operator, he starts to frantically apologize for something that he didn't need to apologize for.
The girl wasn't even asking for an apology, literally just confirming if he actually was the person, albeit a bit disappointed.
It's easy to understand why she was sad or disappointed, but why does she feel the need to make him tell her who he is? He quite literally saved her family from its downfall.
And I mean, why did he not dismiss the cat god's request to tell her everything about himself? The cat god didn't even hear about his reincarnation, I don't think?
If they already get along so well, why do they need permission to help each other? It's like they weren't friends in the first place but just had a forced relationship.
Also, why does she get embarrassed while asking if she can help if he has a problem again?
Apparently saving each other once creates this kind of unbreakable bond, as they both blushed, or were they both holding down their urge to let out a fiery blush as they both shook hands the first time they met?
I'm not saying that this manga is inadequate; it just sometimes doesn't make much sense.