Thank you for the update !
Comment edited because I should have read the dev log before commenting (and getting good was enough in fact instead of diminishing the difficulty) so great game !
Check the dev log. There is no skill tree anymore, instead each character you get to full corruption and get a lewd scene of gives you a passive skill (Which is now viewable in the bar that comes from the bottom left corner). You don't have to make a new game, just go through the first guys and do the lewd scene for each and you can get everything done pretty quick.