Shiki is a troubled and angry teenager, just one bad day away from unloading his frustrations on his entire class. Unsurprisingly, he gets expelled from school for his behavior—mainly because he kept threatening to use his classmates for target practice. Though he pretends not to care about the expulsion, deep down, he knows his life is going nowhere. He figures he’ll probably end up flipping burgers at Mickey D’s for the rest of his life.
Moments later, Shiki’s father storms into the room and smacks him on the head after receiving the expulsion letter. Outraged, he tries to hit Shiki again, but this time Shiki anticipates the move and dodges, jumping onto his bed. His father calms down slightly but still demands an explanation—not only about the expulsion but also about how Shiki managed to collect the guns stashed in his room, since that kind of arsenal isn’t easy or legal to acquire. He warns Shiki to straighten up before he ruins his life.
This strikes a nerve. Shiki snaps back, shouting that he’s glad they aren’t related by blood because he’d never want to end up like his father. That deeply hurts his father, and though Shiki realizes he went too far, neither of them gets the chance to apologize as the phone in the liquor store downstairs rings. His father goes to answer it and is surprised to get a large beer order. Since business has been slow, he’s happy to oblige and heads out in his car to make the delivery.
Once Shiki sees his father leave, he picks up a gun for target practice and mutters about how he wishes things had turned out differently. Suddenly, he hears a loud crash outside his room. Before he can react, he’s dragged onto the street by a rope of black mist. Disoriented, Shiki sees a man named Samidare walking out of the smoke—and he seems to know exactly who Shiki is.
Just then, a car slams into Samidare, pinning him to a wall. Shiki’s father shouts at him to get in the car immediately, and without hesitation, Shiki jumps in. As they drive away, Shiki starts bombarding his father with questions: who was that man, why was he attacked, and how did his father manage to hit someone so calmly with his car? His father explains that someone like Samidare wouldn’t die from just being run over.
Still confused, Shiki demands answers. His father decides it’s time to reveal the truth: Shiki is a descendant of the Oni, while Samidare is a descendant of the Momotaro, which is why he’s hunting Shiki. Before he can explain further, the black mist begins surrounding their car, causing it to malfunction. Forced to drive into an abandoned factory, they escape on foot. But before long, the black mist engulfs their car and it explodes in flames.
In the chaos, Shiki’s father loses sight of him for a moment—and in that instant, Samidare kidnaps Shiki, binding him in the air with black mist. When Shiki demands to know why he’s being attacked, Samidare coldly responds that anyone with Oni blood is a pest that must be exterminated.
Just as Samidare prepares to kill Shiki, his father intervenes. He explains that the legends of the Momotaro and the Oni are real and that their war has been ongoing for millennia. Across generations, the Momotaro Agency was formed by the descendants of Momotaro to exterminate the Oni.
Though Shiki is still confused, his father tells him to stay back while he handles Samidare. As the fight begins, Samidare manifests two swords from the black mist and attacks with incredible speed. Shiki’s father counters with his own mist blade, revealing his familiarity with the technique. The black mist is a unique power possessed only by the descendants of Momotaro.
Here comes a shocking revelation: Shiki‘s father was once a member of the Momotaro Agency himself. His real name was Tsuyoshi Momo, and he used to work alongside Samidare. He abandoned that life to raise Shiki away from the agency’s eyes, but he couldn’t hide forever.
Samidare asks if Tsuyoshi has forgotten how dangerous Oni can be, but Tsuyoshi refuses to engage in that argument—he only wants to protect his son. Despite putting up a good fight, Tsuyoshi is eventually wounded—his chest cut open, leaving him unconscious. Horrified, Shiki yells at Samidare for hurting his father, prompting Samidare to turn his attention back to Shiki to finish him off.
But with the last of his strength, Tsuyoshi grabs Samidare’s leg, asking why he would go so far to kill an innocent child. He declares that a father doesn’t need a reason to protect his son. Shiki might have Oni blood and be a poor student, but he has never hurt anyone.
Tsuyoshi‘s words strike a nerve with Samidare, who begins to feel the weight of his regrets—but he refuses to listen further. He prepares to finish off Tsuyoshi, while Shiki watches helplessly. Overwhelmed by rage and hatred, Shiki‘s body begins to bleed from every orifice. When Samidare looks back, Shiki is no longer there.
Suddenly, Samidare hears the sound of multiple guns cocking near his head. Startled, he instinctively jumps back, narrowly avoiding an attack—but he still has no idea where Shiki is.
Just then, Samidare notices a drop of blood hit the floor. He looks up—and finds an awakened Shiki clinging to the ceiling. Samidare is stunned that Shiki not only awakened his Oni powers but also managed to control his blood so quickly. What makes the Oni truly terrifying, however, is their utter lack of humanity—making them brutally relentless.
Samidare prepares his sword, bracing for Shiki’s next move. But as Shiki starts firing blood missiles at him, Samidare realizes the situation is getting out of hand. He opts to flee, escaping the blast radius—but the battle isn’t over yet. Emerging from the smoke, Shiki lands a devastating kick that sends Samidare crashing into rubble, leaving him barely conscious.
Standing over him, Shiki unleashes his entire arsenal of weapons, destroying the warehouse in a violent barrage. Miraculously, Samidare survives, but before he can recover, Shiki suddenly reverts back to his human form. Confused, Shiki wonders why he’s covered in blood, a natural reaction considering the carnage.
Seeing this, Samidare prepares to strike, eager to finish Shiki before he transforms again. He charges, muttering that all Oni must be exterminated—no exceptions. Shiki, unable to transform at will, is completely vulnerable. As Samidare‘s blade is about to land, Tsuyoshi—Shiki‘s father—throws himself between them, taking the fatal blow.
Samidare is shocked that Tsuyoshi would go so far to protect an Oni. But Tsuyoshi, recalling the precious memories spent with Shiki, doesn’t mind dying if it means protecting his son. Exhausted by the prolonged fight and mindful that the destruction is attracting attention, Samidare withdraws, melting away into a cloud of black mist—the Momotaro Agency must remain hidden, after all.
Once Samidare is gone, Tsuyoshi collapses in Shiki‘s arms. Panicked, Shiki says he’ll call an ambulance, but Tsuyoshi admits that no hospital can save him now—his time is nearly up. He wants to speak with Shiki one last time.
First, he apologizes for keeping the truth from Shiki, but says it wasn’t an easy topic to bring up. Knowing he won’t be around much longer, he urges Shiki to become stronger, to surpass both the Momotaro and the Oni, so he can live a truly free life. Shiki, on the verge of tears, yells at his father to stop talking like he’s already dead. Determined, he lifts Tsuyoshi to carry him to a hospital.
Seeing Shiki‘s concern brings a smile to Tsuyoshi‘s face, but his injuries are too severe. After only a few steps, Tsuyoshi‘s body gives out and he collapses. Shiki desperately begs his father to get up, regretting that he never apologized for the hurtful things he said that morning—but it’s already too late. Tsuyoshi has passed away.
As Shiki sits weeping over his father’s body, someone suddenly approaches from behind, saying Shiki can’t stay there because witnesses are approaching. Startled, Shiki tries to prepare for another fight, but before he can even turn around, he’s struck in the neck and knocked out instantly.
It takes considerable skill to sneak up on someone while wearing roller skates, but this stranger clearly outmatched Shiki.
Meanwhile, the leaders of the Momotaro Agency are in an uproar upon hearing about Samidare’s failure to eliminate Shiki. Some wonder if Samidare has grown weaker, but given the situation, they can’t fault his decision to withdraw—the agency’s existence must remain secret. Regardless, they insist Shiki must be killed before the public learns about the Oni.
However, that plan just became more difficult. After being knocked out, Shiki was taken to a remote island, far away from the public eye. The idea is to enroll him in a school full of half-Oni like himself, where he can properly train his abilities.
Before that, though, Mudano Naito—the man who captured Shiki—needs to evaluate him to see if he’s worth recruiting.
When Shiki wakes up, he finds himself shirtless and tied to a chair. Strangely, the man behind him is doing push-ups on an umbrella—a bizarre sight, but not the strangest thing Shiki has seen recently. The man introduces himself as Naito, and now that Shiki is awake, he begins explaining the situation.
First, Naito reveals his horns, proving that he too is an Oni. He tells Shiki he was brought here for two reasons: evaluation and retrieval. As Shiki already knows, the Momotaro Agency hunts down Oni using their black mist. The man who killed his father, Samidare, was one of them. To fight back, the Oni Agency was formed, and Naito’s job is to find newly awakened Oni like Shiki and assess if they’re fit to join.
Once the briefing ends, Naito unties Shiki‘s mouth so he can speak. As soon as he’s able, Shiki starts yelling, demanding to know what they’ve done with his father’s body. Annoyed by the shouting, Naito deducts points from the evaluation and assures Shiki that his father’s body is safely stored in the facility—but he’s dead, so it doesn’t matter much.
Shiki struggles violently, trying to break free, but this behavior is precisely why Naito tied him up in the first place. Seeing his anger isn’t helping, Shiki calms himself and politely asks Naito to release him, explaining that he has a score to settle with the man who killed his father.
Despite Shiki’s calm words, his face is still contorted with rage, so Naito refuses. He knows Shiki wouldn’t stand a chance against a Momotaro agent yet. But since Shiki is so eager to throw himself into battle, Naito decides there’s a better way to evaluate his potential.
Naito takes off his tie, and before Shiki can react, he sneaks up behind him and begins strangling him with it. This is all part of Naito’s test—Shiki must figure out how to escape, or he dies. Either outcome doesn’t bother Naito in the slightest.
Refusing to die at the hands of some roller-skating jerk, Shiki struggles violently, to the point where blood starts pooling around his eyes. Unfortunately, he can’t break free in time and eventually passes out. Naito is fully prepared to keep strangling him until he’s dead, but just then, Shiki‘s subconscious kicks in, and he enters Berserker Mode. The blood on the floor forms spikes that nearly impale Naito, forcing him to back away.
The moment Naito looks away, he hears the click of a machine gun aimed at his head—Shiki has manifested it and opens fire without hesitation. When the dust settles, however, Naito is completely unharmed. He shielded himself with his blood umbrella, a technique born from his blood manipulation.
Seeing that Shiki hasn’t learned to control his blood powers and only fights while berserk, Naito decides this could be a teachable moment. He plans to subdue Shiki as gently as possible.
When Shiki regains consciousness, his arm is drenched in blood, and Naito stands over him. Shiki has no idea what just happened. As expected, Naito explains that when an Oni goes berserk, they lose all sense of self and destroy everything around them—hence why the room is now a wreck.
Since Shiki still looks confused, Naito assumes he must be an idiot. To clarify, he bluntly tells Shiki that he’s graceless and clueless about blood control. Declaring Shiki disqualified, Naito‘s words leave him frustrated and angry. Yet, even in his frustration, Shiki realizes that Naito is overwhelmingly strong. He knows he can’t beat him, but if he wants revenge on the Momotaro Agency, he needs help—so he swallows his pride and bows, begging Naito to take him as a student.
Naito immediately rejects the request. In battle, fighting without thinking is suicide, and since Shiki mindlessly went berserk, he’s deemed unfit. Unable to control his blood and acting purely on emotion, Shiki is, in Naito’s words, “useless.” Since Shiki failed the evaluation, Naito declares that he’ll have to kill him to prevent a rogue berserker from running free.
Shocked but aware that Naito isn’t bluffing, Shiki bolts, trying to escape. But as Naito prepares his blood umbrella to strike, Shiki knows he can’t outrun him—so instead, he charges straight at Naito.
Naito thinks Shiki has lost his mind, setting up a wall of blood spikes to block him. He anticipates that Shiki will either dodge to the side, leap over, or retreat—standard options against an impenetrable wall. As expected, Shiki jumps over the spikes, but what Naito didn’t predict is that, mid-air, Shiki forms a gun from his blood and fires point-blank at Naito’s head.
Though impressed that Shiki landed a hit, Naito remains unharmed—the bullet wasn’t strong enough. Still, he’s shocked that Shiki managed to control his blood, though he suspects it might have been a fluke since Shiki looks ready to go berserk again.
Preparing his ultimate attack to finish things, Naito is stunned when Shiki suppresses his berserk state and stays in control. Curious, Naito asks how he managed it. Shiki explains that he saw Naito use his ring to cut his finger and manifest his blood umbrella, so he copied the idea. In his mind, he just screamed, “Give me a gun!” and his arm transformed.
It sounds absurd to Naito, but he can’t deny it worked. Typically, Oni must keep their emotions tightly in check to avoid going berserk, especially hotheads like Shiki. But Shiki is different—rather than suppressing his emotions, he seemingly beat them into submission, making his berserk mode work for him. Crude, but undeniably effective.
Shiki then pledges to grow strong enough to kill the man who murdered his father, promising to do whatever it takes if Naito will teach him. Seeing his sincerity, Naito still declines, reminding Shiki that what he just did was a dead man’s gamble with no backup plan if things went wrong. That kind of recklessness is unacceptable.
However, Naito admits that Shiki isn’t entirely hopeless—so he changes his mind. He cancels Shiki’s execution and agrees to take him in as his student. He doesn’t elaborate on what changed his mind, but he recognizes Shiki’s potential and refuses to let it go to waste.
He explains that they are on Anagashima Island, home to Retsu Academy, a military school built specifically for Oni. The academy’s purpose is to train Oni to fight against the Momotaro Agency. While Naito continues explaining, Shiki is more distracted by the fact that he’s on an island, prompting Naito to poke him in the face for asking irrelevant questions mid-explanation.
Naito reveals that he is the homeroom teacher at the academy. From now on, he’ll be responsible for training Shiki and the other students. Shiki will have to live, train, and fight constantly to one day face the Momotaro agents.
Overwhelmed by the sheer amount of information, Shiki can barely process it all. But in the end, it doesn’t matter to him—he’ll do whatever it takes to get stronger and avenge his father.
A little while later, Naito leads Shiki to the changing room to put on his new school uniform. Shiki feels strange—he never thought he’d wear a school uniform again after being expelled from his old school. Naito informs him that there are other students in his class, but warns that Shiki is by far the weakest among them, so he’d better not pick any fights.
While changing, Shiki asks where his father is. Naito explains that they’ve kept his father’s body in the morgue, and that arranging the funeral is Shiki’s responsibility. This reminder dampens Shiki’s mood, but Naito advises him not to dwell on regrets. Instead, he should focus on getting stronger so he never has to feel such regret again.
Not wanting to waste any more time, Naito skates off, telling Shiki that he only has 15 seconds to get to class or he’ll be late. Shiki protests that it’s not fair, but with no other option, he runs as fast as he can.
They eventually reach the classroom door. As Shiki contemplates the coolest way to introduce himself, Naito, fed up with the delay, kicks him inside. Shiki crashes face-first onto the floor, giving himself a nosebleed. Looking up, Shiki asks the first person he sees for a tissue. The student, Jin Kougasaki, coldly tells him to shut up and sit down.
Shiki is immediately irritated and gets in Jin‘s face, ready to argue. Besides Jin, there are other students in the class: Kuina Sazanami, Juuji Yusurube, Homare Byoubugaura, and Akari Momomiya. But right now, Shiki only cares about settling things with Jin.
Before a fight can start, both Shiki and Jin suddenly find themselves seated next to each other with Naito standing behind them. Neither of them noticed Naito move—they’re both paralyzed with fear. Shiki complains about sitting next to someone like Jin, but Naito couldn’t care less about their personal disputes.
Moving on, Naito announces that today’s activity is a game of tag. Shiki is confused, thinking it must be a code word, but no—it’s just a literal game of tag. The students must make their way through the forest to the goal, but Naito will be chasing them. Anyone he catches will be expelled on the spot.
To make things fair, Naito promises not to use his blood powers—although the students can use theirs as much as they want. However, if anyone goes berserk, he’ll be forced to use his blood too, and things won’t end well for them.
Jin asks what happens if someone accidentally kills Naito during the game. Naito replies that if anyone can kill him, they’ll immediately graduate and be assigned to any unit they desire—though he warns that it won’t be easy.
The class is visibly excited by this reward. Shiki still feels hesitant—he’s not used to such extreme situations—but he isn’t about to back down. He declares that he’s ready, telling Naito to bring it on.
