Outarou and MC, if I'm correct, were intended to be written as a character both in need of growth. In the beginning, the MC, being a kid, was overly spoiled and seemed a little bit too selfish compared to other kids. She was fascinated with everything and yearned to grow up fast despite being pretty immature and carefree herself. Outarou on the other hand, was a typical playboy with no care for other girl's feelings. I would say.. Outarou helped the MC indirectly (just a little imo) to grow; he taught her about discovering love, and how to love others. The MC intrigued Outarou with her childness and taught him how to love, which turned him to be a little sympathetic towards the end. That sounds all good though, but to be blunt, the odd age gap was too hard to walk around. There were times where Outarou walked out of legal and moral boundaries, considering the MC is a teenager in her magic form. He even admits to not wanting to keep an underage person in his house without a proper permission from a parent. As much fun I had reading their interactions, I would go so far to say that although he did reject a kiss from her early on to respect her innocence, he could've done a lot better. All in all, Outarou can easily and understandably be seen as a literal creep to the readers, and MC to be a tad annoying. I give the MC some slack though, since after his death, is when it really showed her to be more mature. Lol.
Sanjo and Jin, I wish the author gave more consideration into them as a couple. They practically tied the knot not because one of them had the courage to confess (although I wouldn't really say Jin was in love with her at the beginning), but because of Jin's lust. That's it.
