Shin Megami Tensei: If... Gakuen no Akuma Tsukai

Nobu is just an ordinary high school student messing around with a floppy disk on the school computer when a demon shoots out of the screen and kills his two friends in front of his eyes. Terrified, he runs out of the room to search for his teacher, only to run into classmate Yumi Shirakawa instead. As they try to make sense of the situation, the pair stumble upon their science teacher using hypnosis to convert students into demons!

Claiming to work for the "God Emperor," their teacher begins to target Nobu and Yumi with the intent of killing them both for getting in his way. Trapped within the confines of the school, Nobu tinkers with the floppy disk and discovers that there is a demon summoning program on it. With no other means of defending themselves, the two resolve to use these creatures to fight and return back to the world they once knew.