For me it's not even that i need ugly bastards to steal the girls, i mean sure, i prefer NTR when there is an age gap between the girls and the bad guys but in this case it's more that that, i just simply don't see Kema as a villain, sure he's been beefing with Yui ever since they were kids, but i don't see him stealing not only the girl the MC is in love with but his sister as well. Saying that Kema lives in the MC's shadow is a prefectly reasonably theory but other than that they've been cool all their lives as far as i can tell. Inatari said that 2.3 was done the way it was so that Kema's corruption could begin, so i guess it all depends on how far his corruption will go, but i still don't see him doing anything with the girls, what I would like actually, is for Juvia to go out of her way and start corrupting them, if i'm being a 100% honest i am actually blown the fuck away by her character, i've played a bunch of NTR games in my life but i've never seen a woman who was not only corrupted but was also corrupting other girls right out of the gate as the game starts. Juvia using Kema as a gateway to get to the girls is the only way i can see Kema doing anything with them. The main reason behind my distaste for Kema doing any kind of corrupting however is that he's gonna be on the receiving end of the NTR stick sooner or later when his mother's gonna get "stolen" i guess the correct word is.