Man... this game was weird as fuck...
Not sure what the dev was going for here aside from showing people being horrible. I can't say I feel any real pity for any of the girls, the things they did nearly strayed into murder and at the rate they were going, they'd have likely driven MC to suicide in another month or two if they didn't accidentally kill him. Mainly Hiyori... At the same time, a lot of the MC's problems could have been avoided if he just properly stood up to the crazy bitches and actually talked to his teachers and stuff. That's leaving aside how pathetic he had to be to write that one notebook, or fap at school and hide the evidence in his pocket, or get a boner while being kicked around just because he saw a pair of panties... As such I can't say I feel that much pity for him either, even though the girls went way, way, waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay too far for no good reason.
Especially Hiyori. Man. That bitch was batshit crazy. Did not expect that.
Aside from that though, the game is kinda lazily done. The girls don't have any reactions to the others dying, so the order in which you kill them off in doesn't matter at all aside from needing to push down blondie to 1 heart first before you can reduce any of them to zero hearts. Because for some reason the dev was too lazy to code in MC losing his V-card to any of the girls, and it had to be that specific one...
The gameplay was shockingly easy though. As others said, the hardest part is right at the start, but once you get the cross deletion function, it's fairly easy to herd the 3 into a corner, which limits their movements and access to crosses. After that, you just need to take some turns to just delete and or molest to steal crosses for them, and do cumshot battles only when the RNG favors you and you don't need to waste more than 1 AP to keep them in place. Ez.
After that, just grind revenge points and unlock everything you want at whatever pace you want and enjoy messing with the three of them however much you want.
On a side note, the game does NOT tell you that there's a special ending of sorts that happens if you push all three to zero hearts and don't kill them right away. Which is kind of annoying, but you can unlock it in the gallery right after anyway...