The joke in this is actually how you play the MC. Most times Kalvin "wants to" fuck Angie is simply imagination by the MC! Angela (to the currently here available version) never had any sex with Kalvin nor does she desire it (depending on your choices, sometimes she fantasies about it, but as said depending on your choices earlier).
As I mentioned in an earlier post, you can experiment what you want/how you approach the various girls. You can go for a full harem, you can try to win the heart of just one or two girls, you can become a sharing swinger or you veer towards cuckolding or worse hard NTR.
For instance in one playthrough I go for full romance with Prof. Jennifer and Min-ah, swinging with Angie and Layla (for me she is a real afterthough compared to the other girls). I also have playthroughs where I go full romance with e.g. Angie.