At his old school, Yusuke was considered just another delinquent. Most of the students at his school either looked down upon him, or feared him, for one reason or another. Because of this, Yusuke kept to himself, and became more content with being the bad guy. He skipped out on most of his classes, got into fights with other students, and never respected any authority figures. Because of this, he soon became feared by all the other students, and even hated among some of the teachers.
Along the way, Yusuke began to notice developing powers within him. He didn't know where these powers were coming from, but he didn't really care. He became capable of generating a kind of spirit energy, and he was capable of seeing invisible creatures. Unfortunately, he decides to use his new powers to start even more fights, and he eventually becomes the most infamous boy in his District.
One day, after returning home from school, Yusuke finds his mother, Atsuko, drunk and day-dreaming in the house. This was common for Yusuke; Atsuko never once in her life did anything most mothers should be doing. Yusuke prett much wound up taking care of himself most of his childhood, as well as looking after her, and at this point, he had gotten sick of it. After he snaps at his mother, calling her crazy for wanting to raise a family, Atsuko suddenly breaks down crying. This was the first time Yusuke saw her show that kind of emotion, and it made him feel guilty. Yusuke tries to apologize for the remark, pointing out that she never let stuff he said bother her before. Atsuko is angry at first, telling him she never asked to be a mother to begin with, and blamed it all on a man named Gouki. Then, she explains everything to him, about how she had been raped by a demon, Gouki, and how she wound up impregnated with Yusuke. She couldn't tell the authorities; they wouldn't have believed her. And as soon as signs of her pregnancy began to show, rumors began circulating around the District, mostly hearsay about Atsuko's "heathen ways". She wound up losing almost everything because of it, and found no comfort in anything accept a bottle of sake. At first, Yusuke is shocked by what he's hearing. Learning that he's half-demon explains his powers. But then, the more he thinks about it, the more angry he becomes. He finally understood why the other students and teachers always treated him the way they did. Deep down, he always felt, somehow, that he was to blame for his lot in life. After hearing this, he now knew who was to blame for his rotten lot in life, and he was ready for payback.
After months of searching, Yusuke was finally able to track down Gouki. He confronts his dead-beat dad about the rape. Gouki confirms what Atsuko told him, adding that it was her that begged for it. Yusuke snaps, and engages Gouki in a death battle, intent on killing Gouki for ruining his and Atsuko's lives. At the end of the fight, Yusuke bids his final, bitter fairwell to Gouki before killing him.
After killing his dad, Yusuke is found out by Spirit World Authorities, and is charged with second degree murder. But before he's set to appear in court, Yusuke manages to get into even more trouble. One day, he's cornered by one of his teachers, Mr. Iwamoto. Iwamoto saw Yusuke as nothing more than a liability to the school, and was ready to do almost anything to get rid of him. This day, he managed to catch Yusuke lounging in the halls, dragged him into the teachers office, and proceeded to beat on him, and throw as many insults about him and his mother as he could. Provoking Yusuke into hitting him would be more than enough grounds for Iwamoto to expell him. But, he's interrupted by another one of Yusuke's teachers, Mr. Takenaka. Iwamoto tries to blow him off, but Takenaka responds with a threat to report Iwamoto for abuse, so Takenaka retreats, after one last insult to Yusuke's face. As both Takenaka and Iwamoto leave, Yusuke still feels unsatisfied, so he uses his powers to take his vengeance against Iwamoto. His actions put Iwamoto in the hospital.
The date of his court appearance, Yusuke's case is looked over by Koenma, Overseer of the Spirit World. Normally, Koenma would consider this an open-shut case. However, circumstances make Yusuke's case more complicated, two of the most prominent being that Yusuke's a minor, as well as Gouki's criminal record, which included a number of murder charges. All things considered, Koenma opted not to send Yusuke to jail. In exchange for his guilty plea, Koenma will give him a one year probationary period, coupled with a transfer to a school for special beings, like him. If Yusuke can prove he's reformed, his criminal record will be wiped clean. Yusuke is indifferent to what happens to him, but accepts the deal.
Yusuke, being half demon, developed the ability to generate large amounts of spirit energy. He can also discharge that energy different types of energy blasts from his hands and fingers. He can also concentrate that energy into his fists to increase his punching power.Unfortunately, that power comes at a price for him. Every time he uses his demon powers, it causes increased strain on his body. If he uses too much energy, his organs begin to shut down. Over time, he's been able to train himself so he's able to last longer using his powers, but he still has to make sure not to draw out his fights too long, or he could seriously injure himself. Yusuke also has the ability to detect invisible beings, like ghosts. He can also use this ability to see past disquises, like demons hiding in human form.