Do yourself a favor and play the other games like
Demon Harem (Vanilla) and
Fox Girls Never Play Dirty (Optional NTR and Vanilla), these 2 allow you to have sex with the girls and let your girl get fuck by others or not depending on your decision and outcome of the fight (The fox girls game).
The other reviewers here already described their experience with this game on how bad it was. The game's main theme is NTR, blackmail, and corruption. This game gave me a headache of how bad the scenarios were and the only gameplay here is puzzle solving (baby-level IQ) and RPG fights (which are boring like any other RPG). The game only has 2 endings but you'll see 1 ending twice in order to see the 2nd one. This is basically CG hunting and nothing else, you do see the female character change throughout the story to the point she wants you to be a cuck if you don't unlock the 2nd ending.
The story, TLDR you're experiencing what Subaru experienced in Re: Zero but worst.
Chapter 1: Introduction. You get to fuck the girl at the end but the professor blackmails both and then rapes the girl.
Chapter 2: 1st loop. You met the self-proclaimed Demon Lord (best girl in this game) and made a contract with her to find the one who sealed her in exchange she will help the MC by looping back in time. You found the source of dark magic but got locked up by the spy from upperclassmen and blackmailed the girl then gangbang her.
Chapter 3: 2nd loop. You tried to enter the Magic Research Lab to find the upperclassmen from the previous loop who were trying to use dark magic to gain power. Meanwhile, the effect of looping affects the girl and she voluntarily becomes those senpai's fuck toy without a second thought.
Chapter 4: 3rd loop. After stopping the senpais you were killed by a mysterious person and start another loop. This time the senpai didn't perform any magic circle like the last loop but the new problem is the professor that rape your girl. She was still affected by the previous loop and voluntarily became the professor's guinea pig during class (meaning telling her to do sexual things both on the professor and others who are not the MC). Later on, you travel inside a secret dimension but each time you escape the girl gets transported to the professor's room and he does some experiments on her that change her appearance (her boob got bigger, crotch tattoo, anal). You found the room and fought his pet then saved the girl from being manipulated.
Chapter 5: Final loop. After the professor loop, the girl got mentally damaged so the MC did another loop. This time the 2 threats from the previous loop didn't do anything but you did get a suspicious letter in front of your room with a message saying the girl is your biggest weakness. The girl's appearance is exactly the same as in the previous loop and she becomes the school's prostitute by letting men do whatever they want with her body. This time the girl has a crush on the hot boy in the class and usually has sex with him on many occasions. You found out the mastermind behind the Demon Lord's imprisonment and the different reality of each loop, you fought him then the Demon Lord was free and your girl confessed her feelings to the MC but wanted him to watch her getting railed by every man she laid eyes on.
True end: Talk to everyone and the Demon Lord about the rumors. You need to clear 3 mini-dungeons to get this ending. The location for each is: Under the church > The boy's dorm upper right > On the right outside the school gate. After clearing a dungeon go talk to the Demon Lord to unlock the next one. After finishing those 3, go see the ending again but choose to skip the ending to skip the credit then whala, your true ending.
The art is the game's only saving grace. Just search a save file in the thread or go to www/img/picture to see the images.
The dev can make a really good vanilla game like Demon Harem and Fox Girls's Vanilla route, but NeToRare not so much. Hopefully, in their next work they can make something as good as Demon Harem cause so far most of their NTR games aren't very good if I'm being honest.