Junpei Yoshino (
Junpei had shoulder length black hair which covered the right half of his face (thus hiding his scar), pale skin and dark eyes. From his first introduction, he is either seen wearing a black and white stripped top or a simple white t-shirt with a black rectangle printed on the front with long black pants and sneakers. Later on, after his mother's death, he is seen wearing one of her black jackets in mourning.
The troubles in his life that came about as a result of his negative interactions with his classmates caused him to become a reclusive loner who had no friends. He had an apathetic view towards most of humanity and society as a whole, stating that even if there existed a button that would kill all those he hates, he probably won't press it but if there was a button that would kill every person who hated him, he'd press it without hesitating. However despite his resentment, he takes a liking to Yuji fairly quickly after meeting him.
Junpei grew up with a single mother and had a pretty standard upbringing however, he was bullied by several of his classmates, with Shota Ito being one of them. In one such instance, the end result caused him to end up with a scar on his forehead.
Vs. Mahito Arc
At the Kinema Cinema while watching a movie, Junpei notes the three boys sitting in the front row and recognizes them as three of the students at his school who bullied him in the past. He becomes increasingly annoyed by their incessant chatter and finds himself unable to concentrate on the film. Suddenly, Mahito appears and kills all three students by distorting their heads with his ability. Mahito leaves the theater soon after but Junpei gives chase and manages to catch up to him. He asks the mysterious man before him if he was the one who did it, but Mahito replies with a question and asks Junpei if those boys were special to him. Recalling the horrible treatment he endured, Junpei becomes enraged and asks Mahito if he can accomplish the same feat.
Junpei follows Mahito to his base of operations in the sewer, where they have a conversation about what Cursed Spirits are. Junpei asks what kind of Cursed Spirit Mahito and he replies that he is a spirit that was created from the stomachs of people who hate and fear other people. They continue their conversation, during which Mahito shows Junpei the experiments that he's done on humans so far, showing Junpei the experiments he's conducted to find out how large a human can get but also how small a human can become as well.
Later, Junpei is walking home and finds his teacher, Sotomura, sitting on the steps in front of his building. When Sotomura starts to aggravate Junpei, he motions to activate his power but is stopped by the timely arrival of Yuji. After Yuji creates a distraction and gets rid of Sotomura, Junpei and Yuji head off to have a chat. When they reach a river bed, Yuji asks about the theater incident. Junpei however covers for Mahito and claims that he didn't notice anything of importance at the time and that he could only begin to see curses fairly recently. The two then reach the topic of films after Yuji asks Junpei what movie he went to see and they discover that they have similar tastes in film. When Junpei's mom Nagi approaches them shortly after, he introduces Yuji to her and she invites him over for dinner. After Nagi falls asleep, Junpei asks Yuji what his mother is like to which Yuji nonchalantly replies that he never knew her but faintly remembers his dad. They then discuss what would Yuji do if he had to kill a person like a bad Shaman but Yuji is adamant that he does not want to end another's life because once he crosses that threshold, the value of life becomes ambiguous and he might not even know the true value of those he cherishes afterwards. After Yuji leaves, Junpei does some introspection and comes to the realization that even though he is of the belief that people do not have hearts, he could not kill someone as it would taint his soul.
After Junpei's mother is killed as a result of a curse being attracted to one of Sukuna's fingers, Mahito manipulates Junpei into believing that Shota was the one responsible for it when in fact it was Mahito who planted the appendage in Junpei's house. With feelings of despair and grief still swarming his heart, Junpei goes to school and uses his power to knock out most of the students during morning assembly. Sotomura collapses in shock besides a student and tries to shake them awake, bewildered as to what is happening before his eyes. Junpei appears before him and reassures him that they will not die before turning to Shota, asking him if he was indeed the one who left that at his house.
Unsatisfied with his lack of response, Junpei corners Shota and begins to slowly torture him, starting with partially disintegrating his left arm. Shota tries to apologize but his voice is distorted from all the blood in his throat. Junpei is not swayed by this in the slightest however but before his attack turns fatal, Yuji shows up and stops him.
Junpei and Yuji engage in combat throughout the school. Junpei tells Yuji he has no right to interfere with his business but Yuji refuses, stating that that is not his decision to make. Yuji forcefully grabs Junpei and tosses him outside through a window and Junpei expresses his frustration at the fact that his Moon Dregs poison is having no affect on his opponent. Junpei regains his footing and tries to counter attack but he is easily overpowered and Yuji punches him straight into the building. Yuji tries to reason with Junpei once again and expresses understanding that he might have his own reasons for his actions but demands to know how he can state something like humans have no hearts to his mother's face. Junpei begins to crack and Yuji is taken aback by his pained expression as he asks Yuji if he and his mom were cursed by other people's hearts.
Junpei lashes out and is shocked when Yuji makes no move to defend or dodge and instead chooses to take his attack. Yuji apologizes and asks him to explain what happened. After being told the truth, Yuji is left heartbroken and asks Junpei to join him at the magic college where he would be able to meet a great set of wonderful people who he can rely on, reassuring him that they will definitely find the person who cursed his mom and punish them.
However, their moment of reconciliation is abruptly cut short as Mahito suddenly appears behind them on the stairwell, much to Yuji and Junpei's surprise. Yuji asks Mahito who he is, but the man ignores his question and simply begins with a greeting, referring to Yuji as "Sukuna's host" before restraining him with one arm. Yuji screams for Junpei to run away but Junpei, still believing the facade he was shown, stays and tries to mediate the escalating situation, claiming that Mahito was in fact not a bad person. However as he says these words, images of Mahito's experiments flash in his mind which causes Junpei's voice to die in his throat as he seemingly realizes that he's made a grave mistake. Mahito places a hand on the now shaken Junpei's shoulders and taunts him, basically calling him an impulsive fool who is next in line in stupidity after the same people he liked to make fun of.
But before Junpei can even blink, Mahito uses his Idle Mutation technique and transforms Junpei into one of his many ex-human abominations. Yuji is so shocked he is unable to react and the now mutated Junpei gets a hit in, but Yuji ignores the pain and instead focuses on trying to wake Junpei up. Desperate and out of options, he tries to turn to Sukuna for help but is swiftly denied and mocked by Sukuna himself as well as Mahito.
Yuji, now at a loss for words, can do nothing more but watch as Junpei slumps to the ground, grasping at his clothes and faintly asking "...Why...?" before falling to the ground and dying.
Cursed Power and Form
Even though he was not a Shaman he possessed magic and could see curses. He uses his magic to summon a jellyfish shikigami to manipulate the poison created by him.
- Junpei ranked 9th place in the manga's 1st Character Popularity Poll with 7,481 votes.