Trinity Seven

Arata Kasuga, a high school student, is being targeted by a girl with humongous boobs. In exchange for his life, Lilith says that she can erase his memories, but he chooses the third option. As a result, he ends up at a magic school, but why is there a naked girl in the men's bath?

In order to become a mage, you need a research theme which archives one of the seven deadly sins. While thinking about what his theme will be, Arata and 3 others are locked in a barrier, with no exit to be found. But then Lilith and the others find themselves needing to use the restroom... Good luck, girls!

It's summer. The gang's on a southern island, and there's cute girls in swimsuits abound. Arata's cooking yakisoba for some reason, but these things happen. The quartermaster is repairing the school that Arata destroyed in his collapse phenomenon. The girls enjoy a mixed-gender bath, and the demon lord candidate decides on a theme--control.

A power leaks from underneath the school, Arata and the gang head down into the labyrinth to protect the school from the collapse phenomenon.

The girls are running in their exercise outfits, with the boobs swaying to and fro. Arata's heart races. Everyone's having great time, and then a ghost appears in the library. Arata and the gang go to check it out, and are forcefully transported to the "Eternal Library". There they find the lost Trinity Seven!

Liese, the last Trinity Seven, appears in the Eternal Library bearing a demon lord seal, making her a demon lord candidate, as well. She tries to entice Arata to join the evil mage side to help save Hijiri, and kisses Arata while he's unsure what to do. Arata has his magic stolen from him, and Liese decides to attack the school.