I can understand your point of view, but not because he can see her as a romantic interest, it has to be kinky.
Furthermore, it would not be the first couple in which a "minor" is shipped with an "adult".
And it's not like anything beyond a pure relationship is going to happen, yet I respect your opinion
A relationship cannot be pure if it is built upon two members of differing mental stages and appearances, because no matter how little the romantic interaction the child can't consent. Therefore the relationship couldn't even be romantic.
Since you're really shipping just to have fun, you should try to ship things you know are less illegal. Like, atsulucy or shin soukoku or something. Maybe kenji and kyouka? Or Q and kyouka? I don't ship any of those but you get the idea.
Ahhhhhh! I just love how much Atsushi's worried about Kyouka, I can see the love! .
I can't wait for the next chapter! (≧∀≦)