The true identity of the urban legend "Mary-san." She carries a knife and kills her targets after delivering her final line: "I'm right behind you now." Species: Yokai (Satori) Ability: Manipulation of the unconscious She has wavy, light greenish-gray medium-length hair and green eyes. She wears a raven-black hat with a pale yellow ribbon tied on the front-left side. 《List of Lines》 1. "I'm at [Location] now (somewhere very far away)" 2. "I'm at [Location] now (somewhere a bit closer)" 3. "I'm in front of your house now" 4. "I'm in front of your room now" 5. "I'm right behind you now (directly behind)" She gradually gets closer with each call. Anyone who dials the phone number "514" becomes a target for "Mary-san" (Koishi).

Species: Yokai (Kasha) Ability: Carrying away corpses First person: I (casual/tomboyish) She has deep crimson hair styled in braids on both sides, tied at the roots and ends with black ribbons. Her hairstyle is pigtails with straight-cut bangs. Her eyes are also red. A member of the Komeiji Detective Agency and Satori's assistant. She has excellent senses of smell and sight, allowing her to track scents and pinpoint a culprit's location. She can see clearly even at night.

Species: Yokai (Hell Raven with Yatagarasu) Ability: Manipulation of nuclear fusion She wears a white blouse and a green skirt. She has long, wavy black hair adorned with a large green ribbon. A member of the Komeiji Detective Agency and Satori's assistant. She has superior senses of hearing and touch, which she uses to listen in on conversations and take notes.

High school students all across Japan. Every year, several students go missing after trying to test the Mary-san rumor. They often hear about the legend through the internet, and "Mary-san" occasionally becomes a major fad in schools.