The only thing HS Tutor shares with KoS is that both games use koikatsu models(and even models in HS tutor are way inferior!). Otherwise HS tutor is like, the furthest thing possible. Animations in HS tutor are bad and often misaligned, the story is nonsense, every single character is a piece of cardboard, and generally the game is very bad. I played it once and it was a total waste of time. I wouldn't recommend it to my dog. Harsh but true.
Also I am not gonna even say how long HS tutor has been in devleopment. Just enough to mention that it's been several years and it has several times less content than this game. That's where I turn off the mic...
Have to accept that there is no other good koikatsu game like this one currently.
So let the ntr flow through you and enjoy KoS.