I did played years ago, this was iconic classic vanilla game when I last played and by the looks of tags this is no longer that game. It seems like MC can no longer satisfy his daughter so he takes help from friends. Man, the developer really trolled those guys who actually grinded points and build relationships with the characters just to share them with other men.
Well, any sharing path is fully optional and if you don't want it, it doesn't happen.
On the other hand, as you mention points grinding, it does make sense that corruption does not end in vanilla sex happily ever after. Because there is always something more. If teaching an inexperienced girl to give you a handjob is corruption, all the way to vaginal sex, then on to anal, then a corruption theme is likely to take it further: FFM threesomes, MMF threesomes, sharing, stretching, pissing, bestiality, BDSM and a host of other ever more extreme fetishes. In the end, at some point, it always ends in something really unpleasant.
Which I why I dislike the term "corruption" when it should be "romance". But "romance" is, interestingly enough, not in the list of tags....