Affectionately called "Dai-chan" by Cirno and her other Terakoya friends. Originally of a gentle nature, she looks after Cirno. Lately, she has been on the verge of a breakdown due to the sheer number of wicked people, so she has decided to ruthlessly execute judgment on them with her holy sword.

Freezes wicked people. Her reason for doing so is simply "because it's fun."

Seeking to erase all poultry dishes from the face of the earth. If she catches someone eating poultry, she destroys their eardrums with ultrasonic waves. Despite her youth, she runs the Mystia's Izakaya. Naturally, there are no bird-based dishes on the menu. Her full name is Mystia Lorelei.

Visits anyone who has killed an insect, knocks them unconscious with a Rider Kick, and then injects them with malaria. She is a firefly... not a cockroach.

Doesn't care what it is as long as she can eat it. She eats humans.