Well since this is an erotic game, sex is not an indecent act in public but people have different reaction to it. They even do it for a movie or work if they have some kind of affection towards the person they are having sex with.
It contains heavy spoilers for Magic Ring game.
But there are horny people in the world. All male protagonist (Ken from CB, Ted from this game, Mac from Magic Ring), for obvious reason will sleep around with every one.
None of the female protagonist(Anko, Hailey) and their spouses cheat on each other. But there are side character who are super horny, such as Sabrina and Yumiko. You will notice Ted mentioning Mrs. Dahlia (Tall lady) letting him and his friend fuck her ass because for a reason but I can't explain it for plot purpose. Jennifer lies about her sexual endeavors.
About some controversial characters, Luna does let Mac fuck her ass so she would have his ability to program. But remember I told you Mac will be protagonist of Magic Ring. So if anyone has sex with him or watch him having sex with their eyes (not photo or mirror) will have some feeling for him along with their current partner because of ring's effect. Now you may ask why have such weird perk for this ring. It's because this way I will be able to get some kind of gameplay to Magic Ring game when it is launched.
About Ted, he will only love one character, Wendy. Others are just his side chicks. There are characters who has one side love for him such as Luna(thought Ted loves her when he first fucked her), Irene (because of Ted in her universe saved her), Liz (because he help her get rid of his boyfriend) and Nina (has crush on Ted).
Why Harleen, Tess(she does in current demo but will not longer in next update) or Jennifer don't fuck Ted? Because Tess has crush on Mac since childhood. Harleen saw him having sex with Luna and Jennifer saw him with Tess and because of ring's magic they fallen for him.