So, if I understand this game correctly, without cheats, there are only 3 ways to play:
1) Maxing relationship with Kassie, in which case you should not get Kenny involved and go for her solo, or rather, there is no point to involve Kenny, because most of his interactions with Kassie raise her arousal but you have to choose between that or raising her relationship.
2) Maxing Kassie arousal, in which case you should involve Kenny and double team her, since some of the actions that raise arousal are Kenny exclussive.
3) Ignore Kassie and go for Mia.
Regarding 1) and 2) it seems like there is no middle ground, if you don't go full out relationship or full out arousal you just miss on both types of content. Same thing for 3) there is no middle ground between Kassie and Mia, if you are going to have any meaningful interactions with Mia you will miss on a lot of either relationship or arousal with Kassie.
