Trinity Seven follows Arata Kasuga after the bright red sun stops shining and the mysterious Breakdown Phenomenon destroys his town, seemingly erasing the people who lived there. With the magical grimoire left to him by his childhood friend and cousin Hijiri Kasuga, Arata manages to reconstruct his world in an artificial form, but the fragile peace only deepens the mystery behind what really happened.
When the magician Lilith Asami appears to investigate the incident, Arata's artificial world suddenly disintegrates again. He is given two choices: hand over the book, or die. Instead, he chooses the third option and enrolls in the top-secret Royal Biblia Academy, a school for magic users where six other powerful girls are already waiting. Together with Lilith, they become the Trinity Seven, the elite group of the academy, each member mastering a different kind of magic.
As Arata trains with his new allies, he keeps searching for the truth behind the Breakdown Phenomenon and for a way to save Hijiri, refusing to let the loss of his hometown become permanent. Within Royal Biblia Academy, he must also learn to navigate a world ruled by magic, trust the seven girls who stand beside him, and keep moving forward as the mystery behind the Breakdown Phenomenon grows more dangerous.
