IIRC this started out on Ren'py but was moved over to Unity due to some Ren'py limitations which lead to the first reboot, he's not going to go back.
I haven't played this in a while but I'm going to guess there's an uncapped frame rate and Waikus needs to enable VSync, in the meantime use RivaTuner or add it to the NV Control Panel and cap it to fix that issue.
It's been almost four years and it's always been a sandbox, judging from your join date you've been at least lurking here for a while so... What's the point of your post aside from pointless bitching?
This was never Ren'py ! We all told him to move to that engine, but he chose crappy Unity instead... the original version of the game back when it was still "School, Love and Cousins" was an engine called Visual Novel Maker, or Tyrano.. I would know I still have that version (since when he moved to Unity he eliminated more than half the scenes, and made the MC more of a wimp and a perv).... seems he is doing that again with this reboot...
At this point this game is dead to me... removal of incest on an engine that is super hard to patch "original relationships" back, and he keeps making the story dumber (more realistic) by making the MC more unlikable and pervy... just why ?
The story was fine originally dude couldnt be super special awesome as he was the "new kid at school", so he had to work his way up the ladder, but he was friendly and just "cool" enough to slowly win over even people that didnt like him or barely gave him the time of day. Also a few people approached him from the first day (you know like in RL new kids arent hated just for being new !!).
This reminds me of "A New Life" the story was 60% done and was decent, then the dev thought to himself "I should start over and make the MC more of a loser and everyone hates him at the start, that will be great !"....