I can understand having shitty, neglectful parents resulted in a girl like Aika desperately desiring attention, but I don't know about MC being 'different' from other men she has met up to now. This really was only brought up because his ex came along and wanted to get back together with him, and the competition led to her getting the MC out of not losing something (yes, not someone, something) she had in her possession first instead of genuine love, and went all the way with him both out of winning the competition and getting that desire for attention sated. Even during the morning after their romp, she acted like she did during her elementary school days, and I wonder if she would grow out of and get tired of MC after this like she had for those boys back then. We don't even know what her body count was up to this point.
Well, we'll probably never know even in the final chapter next, but one thing we all know for sure is that these three in a love triangle had pretty shitty standards for dating and how to behave when dating, and will probably continue to fumble in these more as they go about their lives.