Jin (ジン, Jin) is an OPT and childhood friend of Jio, who's parents were killed by Satan.
Jio's childhood friend that protected Jio when he was bullied by other kids. The same day that Jin told Jio they were friends, Jin witnessed his parents being killed by Jio in Satan form. He became extremely hateful towards Jio and wanted to kill him.
Jin later became an O.P.T. and was hired by Sabaki to get rid of Lang at Thorn Ruins. For testing his skill, Sabaki put the Umbrella Brothers to fight Jin, and he easily killed all 3 of them. Later when he went at the Thorn Ruins, to his surprise he found that the OPT kid the Umbrella Brothers was talking were Jio. He told Jio that he can't never forget the face of the person killed his parents and that he wants to avenge them. Jin then activated his O-Part and used a Black Flame Pillar attack at Jio, but he was able to dodge it. Jin immediately then rushed and kicked him, sending him in the thorns, where before he followed him, told Lang that he will kill him after Jio.
Inside the thorns, he looked for Jio and was able to dodge his surprise attack from his boomerang, but wasn't able to dodge his kick that followed. As the fight continued, Jin explained the effect of his O-Part and that his hatred for Jio was creating his black flame. Jio again used the same attack: boomerang followed by a kick, to land a hit Jin. While wondering what's Jio's O-Part effect he started his Black Flame Dragon attack, but at the same time, Sabaki who came to the ruins shot Jio in the shoulder, which was enough to distract him so that Jin was able to hit him with his attack. As Jio was pierced and started to burn from the black flame, Jin got angry at Sabaki for interfering his fight, but Sabaki told him that there is no rules in fights. But then the black flame on Jio, died out, which surprised Jin and Jio turned into Satan. Looking at Satan and his number on the forehead, to remembered him as realized it was truly him to killed his parents. Satan found Jin hatred to be a bore and showed him what a true hatred is, and created a black flame that engulfed the whole thorns. As Satan explained that Jio didn't know about what he was doing, Jin realized that this wasn't Jio, but the devil. He remembered his past with Jio, and wanted forgiveness for the things he have done to Jio and in the same moment, Satan stopped who were rushing at him to hit Jin with his black flame coming from his hand. Jin saw Satan turning again to Jio, and that the hatred around him fading away. Jin then took Jio and using his Black Flame Dragon, to extend his sword, he was able to put Jio away from the burning thorns, getting him out of there and saving him. As he was falling down, he was happy that was able to save Jio and that he will finally be able to meet his parents.
Post-time-skip he is seen travelling with Futomomotarou after being saved by him during the Rock Bird arc. They can combine their fire and gas attacks to create a large explosion. Recently it has been revealed that Jin is in possession of one of a recipe nuclei of a demon which he says he personally single handed fought and beat. It was revealed that it was a fake recipe made by Jack.
- Ashura: A large sword which has the effect of releasing fire. Jin has used two types of fire: a black flame which burns everything that it touches and cannot be extinguished, when his heart hold hatred for Jio and, after he forgives Jio, Jin can use a much more powerful blue flame which is at the maximum heat that fire can burn at, more so than normal red or orange flames.
- Black Flame Pillar (黒炎柱, Kokuenchyū): A technique that creates a black flame pillar send forwards that burns everything in its path.
- Black Flame Dragon (黒炎竜, Kokuenryū): A move in which Jin extends his O-Part sword with the assistance of the black flame's heat in order to pierce his enemy. The technique also uses his black flame, which will burn everything that it touches and can't be extinguished.