A bully who Rin fights with and is later possessed by a demon.
- Adaptation Expansion: In the manga, both he and the demon that possessed him were not only defeated after Fujimoto exorcised him once, but they had No Name Given. In the anime, they showed up for a second round in episode 2 before Satan possessed Fujimoto. Also anime only the demon was identified as Astaroth.
- Adaptational Badass: In the anime, he is explicitly stated to have been possessed by Astaroth, the Demon King of Rot.
- Adaptational Villainy: In the manga, the birds he was torturing weren't shown in too much detail, but in the anime, he was shooting them with a crossbow. His retaliation against Rin in the manga was him trying to cut his hair with a knife. In the anime, he tried to brand Rin with a rod he dipped in fire.
- Berserk Button: Rin is this for him in an OVA, as the mere thought of him enrages him enough to allow Astaroth to possess him again.
- Chuck Cunningham Syndrome: Though he should be in the True Cross Academy he has only been seen in an anime extra since his exorcism.
- Disproportionate Retribution: His actions that got him possessed were because Rin punched him in the face.
- Jerkass: He was introduced shooting doves with a crossbow in a public park (Anime) or pinning them down to cut off their legs (Manga).
- Jerk with a Heart of Jerk: In the anime, he was about to pay his friends back for borrowing money from them. Then he beats the crap out of them when he realized they were trying to rip him off.
- Rich Bitch: He gets in True Cross Academy because of his family's connections, and tried to bribe Rin to keep quiet about him killing birds.
- Screw the Rules, I Have Money!: After Rin confronted him, he tried to bribe him to keep quiet so that his family's reputation doesn't get threatened.
- The Sociopath: He kills birds for fun, and tried to scalp Rin in the manga, or tried to brand him in the anime, just for punching him in the face.
- Starter Villain: The demon used him to try and find Rin to take him back to Gehenna, thus leading to Rin's awakening and starting the plot.
- White Hair, Black Heart: Both before and after his possession, he's a jerk with white hair.
Izumo's first friend and a former cram school student.
- Childhood Friends: She has been friends with Izumo since elementary school.
- First Friend: She was the first and only friend Izumo had for most of her life. Once Paku leaves cram school, however, Izumo finds other friends like Rin and Shiemi.
- Last-Name Basis: Everyone, including Izumo, uses "Paku" when referring to and talking to her. The only exception is Shiemi, who refers to her as "Nori-chan" at times.
- Morality Pet: Towards Izumo, though it took Paku a while to object to how Izumo badly was treating Shiemi, who only wanted to be friends.
- Nice Girl: Very much so, as she's the first person in Izumo's life to befriend her and is quite capable of looking past her harsh exterior. She's also willing to call Izumo out for taking advantage of Shiemi.
- Romantic Two-Girl Friendship: With Izumo, but she happily ships her with Rin to Izumo's chagrin.
- Satellite Character: Very little is known about her aside from her friendship with Izumo and is rarely seen without her.
- Shipper on Deck: A special version who encourages both Shiemi and Izumo, despite the fact they share a Love Interest.
A normal True Cross student who Rin wants to make friends with after learning how he started seeing demons.
- The Everyman: Which is what made him seeing Demons so strange.
- I Just Want to Be Normal: His reaction to seeing demons, leading Rin to look for a cure for him. Later defied since after Rin gets the "Demon Eye Drops" Godaiin chooses not to use them.
- Last-Name Basis: Rin only refers to him by his last name. Hilariously, it was bad enough that one of the questions asked of Kato was what his first name was.
- Nice Guy: He quickly accepts Rin's half-demon status.
- Satellite Character: His entire presence in the series is mostly to give Rin a friend outside of cram school and to give a hint to what the Illuminati's plan is about.