Known as "Kawajiri" (川尻), he briefly went by the name "Asu" (アス) during his time as a Devil before being demoted back to a Magic User by Chidaruma. He is Nikaido's adoptive big brother. He became a devil during his adolescence (at 16) and retained his appearance from that time.
Magic User Form:
He has spiky black hair with a tiny ponytail, black marks surrounding his eyes and nose.
Leather mask with a pig snout wrapped around the base of his head and a giant black horn sticking out of the top of his forehead.
Kawajiri always worries about Nikaido, but keeps a calm and collected exterior. Before his Devil Exam, Kawajiri used to be a caring and gentle person, taking care of Nikaido (and worrying about her hardcore training with Yakumo, at the age of 4 years old).
After attaining his devilhood, his personality was warped into the likes of a Devil, becoming brutally honest, mocking people inferior to him, pointing out the flaws of those around, and showing no respect for anyone. Even after losing his Devil status, Kawajiri still retains these aspects of his personality as well as certain preferences, like eating greasy food, only wearing expensive clothes, and listening to Haru's music albums.
An orphan raised by an elderly couple in a forest, Kawajiri used to have two little sisters, Yakumo and Nikaido. He took care of them while ensuring they didn't get in trouble and protected the girls from hunters who kidnapped or killed children in the forest.
When he turned sixteen years old, a Devil approached him to apply for the Devil Exam due to his unique and powerful magic. He soon after left his home, his parents proud of him and wishing him to succeed. Yakumo feeling sad about his departure, giving Nikaido the suspicion she maybe had some romantic feelings for him.
Due to Nikaido's interference with the past with her time-travel type of magic, Kawajiri never met her, nor his foster parents. Consequently, he was raised in an orphanage of the Devil's church. He still took the Devil Exam, and his body was starting to morph into a Devil. But during the Blue Night season, few days before his full transformation, Kawajiri was assaulted by Magic Users who wanted him for his rare magic. He had little to no choice between using his magic to protect himself, losing his chance to attain devilhood, or becoming one of the Magic Users' partners. At that moment, a little Nikaido appeared, saving him by single-handedly beating all of them.
After his transformation was complete, a thankful Kawajiri, now reborn as "Asu", took Nikaido from the streets and helped her go to Hole. Finding out about her mysterious and powerful magic, Asu hid her existence from Chidaruma, the most powerful Devil of all, since he knew she would be harassed for a partnership in the same way he was, if not worse. Preparing her as much as he could, which is seen in a flashback depicting Nikaido in a black-belted karate uniform being trained by Asu, and finally giving the little girl a mask to enhance her power, in case of great need. They parted ways, though promising they would keep in touch with each other.
(Nikaido visits him in his luxury house, bathed with him in hot springs and still showing the same love as a sister as she used to).
Years later, and now back in The Magic User World, Asu was approached by Nikaido. To ask him for help in finding out more about Risu (a man that Kaiman claimed to be a link to his past). Nikaido paid an enormous sum of money for a brief chat with the powerful and demanded Devil. Though he was pleased to see her again, he wasn't able to help much, as there hadn't been any information about Risu among the other Devils that he could pick up. When Asu expressed concern about how far she would go to help Kaiman and how dangerous it could end up being for her, Nikaido only replied that Kaiman was her friend and would support him in any way she could.
Later, Asu sensed that Nikaido had been kidnapped by En to become his partner, but was left unable to do anything without being noticed by Chidaruma. He could only feel sorry for her as he saw how Chidaruma opened her chest for En to sign a partnership contract with her.
He approached Kaiman in Hell's prison, explaining that Nikaido was in danger and that he was the only one capable of rescuing her. Asu was able to save Kaiman and the other staff members of Restaurant Tanba before they were sucked to Hell along with Shimizu, a Cross-Eyes sentenced to death.
After a confrontation beneath the collapsed Devil Church inside En's Mansion, Asu transformed Chota into a clone of Nikaido to help her and Kaiman escape as far away from En as they could to ensure the now damaged contract inside her would never regrow. Leaving after that to confront Chidaruma, Asu realized that Chidaruma had always been aware that he had hidden Nikaido's existence since he was omniscient. The Devil Lord punished him for keeping secrets from him, savagely beating Asu and stripping him of his devilhood by using Store, a powerful creature with knifes growing from its back. Having been on the receiving end of the only weapon in any reality capable of damaging a Devil, Asu's Devil body was torn apart. He felt like a pig in a butchery. His severed body parts sold in the store near Hell, leaving him as Kawajiri with his comparably much smaller Magic User body once again.
The flayed Magic User knew the spell he had cast on Chota would dispel soon. So, he teleported as fast as he could to rescue Nikaido but was too late, as En once again kidnapped her. Weak and injured, he could only save who he supposed to be Kaiman and fainted near a forest with the presumably dead or dying man.
A month later, Kawajiri woke up in an abandoned house near a masked man who presented himself as Aikawa, who he believed to be Kaiman, although the man denied it. After Aikawa used a lot of magic bandages on him, successfully mummifying him to ensure his skin regrew, Kawajiri teleported himself to En's mansion to look for Nikaido, taking Aikawa, who grabbed him in the last moment, with him. There they found Nikaido in a deplorable condition, as her strong will and resistance made her body rot from the inside out instead of regrowing her contract with En.
During the ensuing chaos, after Aikawa disappeared and The Cross-Eyes' Boss returned and killed En, Kawajiri took Nikaido to live with him in his luxury house, where he explained to her that she no longer needed to fear her magic, and instead had to reclaim all the things she lost due to her own power, promising to help her improve her control over it. During their training, which he designed similar to his Devil Exam since the pressure in the Magic User's body caused their magic to become stronger and their minds more focused, Kawajiri gave her a heavy impractical armor. It was twice as heavy as the ones usually used in training. To get her powers to increase, he often sparred with her and even bought his own severed Devil body parts back from the store to make dinner, much to Nikaido's disgust.
Kawajiri explained that no one knows how time travel magic works since there are almost no historical records of Magic Users like her. Nikaido told him about a secret door to En's Mansion room where they could find an old book about her magic type. Disguising themselves as Cross-Eyes and temporarily changing their gender appearance, they sneaked into the En's mansion (now controlled by the Cross-Eyes), where they found Risu and Aikawa. After retrieving the book, though, before Nikaido could talk to her former friend once again, Aikawa left Risu alone with them before losing his senses again. They departed from the mansion with the frustrated Cross-Eyes and returned to Kawajiri's house, where the three of them then lived together for a while.
Kawajiri, thanks to his mischievous nature as a former Devil, teased Risu all the time for being poor. A Cross-Eyes, unable to produce smoke and not being useful at all, though he didn't do it out of malice, he tried his best to patch things up with Risu. But every time things just got worse between them.
Nikaido eventually perfected her control over time travel magic, creating a magic time machine box, and destroying Kawajiri's house in the process. They headed to Hole and lived in the Hungry Bug for a while, where Kawajiri helped her to rewrite her past by saving Yakumo from drowning in the river near the house where they originally had lived together. After they returned to the present, they found out that Nikaido's magic has a limit and that her magic box works like a shotgun, with cartridges as heavy and hard as diamonds that disappear one by one after she travels through time.
Nikaido's newly developed Devil powers made the food she cooked so tasty, that it could almost destroy the nervous system of anyone who ate it. So Kawajiri and Risu were the first victims of Nikaido's delicious, but shocking Gyozas. They decided to head to the Central Department Store to sell the remaining ones, where Kawajiri barely knew how Human money works and put a ludicrously high price on the gyozas. Though the humans inside the department store found this outrageous, they still couldn't resist buying all the gyoza bento boxes anyway. After a power blackout in the entire store, all the humans suddenly disappeared. Kawajiri tried, although unsuccessfully, to teleport them out of the store and away from any danger. But due to the Department Store now being located inside the lake of refuse, the quickly spreading evil influence canceled out his clairvoyance so that they just ended up a few floors above from where they were before.
Now blind and fingerless he found a horde of zombies invading the store (one of them cut his fingers to prevent him from creating a door to the Magic Users realm) and subsequently was capture with Risu (transformed into Curse) by one of the tubes that control the monsters. Realizing their situation, he told Risu that Curse is not him, its merely a power that he can control, with determination. Risu dispelled Curse and was free from the tubes. Thus, leaving Kawajiri alone, crying for help until GuraGura found him and brought the scared Magic User to the Devil party as a petition made by Chidaruma (expressing regret for stripping Kawajiri from his devilhood, just because he was the only Devil who knew how to cook gyozas for him). Chidaruma healed and created a chef outfit for him and a workplace with ingredients demanding to prepare some Gyozas for his party. Kawajiri only could agree with this, knowing the consequences of making Chidaruma angry.
Once the food was ready, the Devil thanked him for it. Then stave off Kawajiri's eyes with his fingers, Duston (apologizing for this) chopped his hands and threw him to the battle between the Magic Users and Hole's avatar, Kai. Chidaruma explained to him that even in this situation and condition, he still had a role in this game.
Noi healed him in the chamber and, together with the rest of the Magic Users presented there. Kaiman and Nikaido (almost fully morphed into a Devil) saw how Aikawa and Risu killed the last head of Devil Kai. Its death released Risu from his curse, leaving him angry and desperate. Once again, he becomes a useless person unable to produce smoke (Kawajiri found this hilarious and mocked him for it).
The whole room became pitch black, and acid started to flow through the floor, in the last moment Kawajiri used his magic to save only one person, Nikaido, apparently dooming everyone else in the room to die.
He's later shown to have survived by teleporting to The Black House, only able to grab Nikaido as he escaped, leaving Risu to his apparent death. Once they were inside the house, Kawajiri was surprised to see Store once again. Now he was exhausted after demoting all the Devils who once were at the party.
After a brief mean spirited and silly-looking dance to despise and mock those who caused harm to him, Kawajiri told Nikaido that they would need all the help they could look for, as the creature that was just born from the lake of refuse would seek their deaths.
He then helped the now fully transformed Devil-Nikaido face off against the creature, but ultimately getting killed alongside her after failing to teleport into the black house. Their dismembered heads now being stuck into the horns of the creature.
After the fight against Hole, his head was resurrected by the Devils (probably Haru) and reunited with Nikaido, Risu and Kaiman.
A half year later, when Nikaido and Kaiman was just walking down to the street where Nikaido discovered Kaiman, Kaiman pointed to the alleyway where Risu was standing (Kaiman's first memory) Nikaido and Kaiman surprised because Risu's shadow was actually there. Suddenly Kawajiri's and Risu's head appeared. Nikaido asked why they were there. Risu stated that they came back to see Kaiman and Nikaido again and to see Hole one more time. Kawajiri said to Nikaido that he and Risu will take another devil exam because he see the potential in Risu. Kawajiri said that they both won't be seeing Kaiman and Nikaido for a while, that's why they came back.
Risu said his goodbye to Kaiman. Nikaido hugged Kawajiri, gave him a hug and said "Goodbye Kawajiri, my big brother." After that, Risu and Kawajiri left Hole using Kawajiri's door. Leaving Nikaido with Kaiman.
- As Asu, his magic door was a regular looking door with a Devil symbol in the lock. But after his demotion to a magic user, his door was an elaborate Chinese gate, adding more to his evidently Asian motif.
- As Asu, his hobby was creating rings based on his close friends. He proudly displayed one of Nikaido made of diamond on Haru's Hobby Channel (An devil TV show mentioned in the Extra Evil of Vol21, ).
- Apparently he has only used his teleportation magic by holding his hand in a salute gesture to use clairvoyance to target his destination.
- His pig-like appearance as the devil Asu is a foreshadowing to how he would be butchered in the store.
- Asu's name "Kawajiri" uses the kanji Kawa(川) meaning river and Jiri(尻) meaning buttocks