Correct me if I'm wrong but afaik the pleasure is not as much related to actually the size of the junk but seems to weight a lot more to the fact if the character likes specific type of sex, i.e "Fucking" (Vaginal) or "Anal". If you manage to get their pleasure into decent levels at least once their related stat will increase more towards liking it and next time the sex will give better results.
Part of the game's appeal is training a random police officer or tech CEO who only likes riding cowgirl into a cocksucking addict through manipulation. It may become more clear further into the game's development as more mechanics are fleshed out I reckon, right now it's more of a detailed relationship life sim, but somewhere down the line I would imagine (Just from the promotional/main menu screen aesthetics and literal game name) that there will be more options and ways to socially hack and manipulate people.
Wouldn't be surprised if there comes a time when you can maneuver around social barriers and NPCs opinion of you in more indirect ways, like having people who are really into you uphold your reputation/spread your name, or engaging in the same hobby as another person (Sports with them in the park, games at home, buying clothes with a plus 1 for fashion, etc etc) and maybe philanthropy or "answer question with answer that suits their personality" type mini-games in conversation. Right now, unlike many initial projects that flesh these things out first, Golden Crow seems intent on shaping the bones and skeleton of the game first, which is the right call for attracting fans and attention.
Right now the most fleshed out parts of the game are the basic stat tracking, genetics system for variety, and of course the fucking. Correct call so far as making a career out of development is concerned, imo.
