Pochita/History

Intro arc
One day, both are mortally wounded by the Zombie Devil and his Yakuza-turned-zombies. Pochita then entered Denji's body, assuming the role of his heart, while repairing Denji's damaged or missing organs and body parts in the process. Pochita is last seen communicating with Denji internally, communicating his wish that Denji show him more of his dreams in exchange for being his heart.

Eternity Devil arc
Pochita's past as the Chainsaw Man is briefly alluded to when the 4th special division team is fighting the Eternity Devil. There, Denji notices that Eternity is mysteriously afraid of his chainsaws, and thus, is avoiding direct confrontation with him, asking for Denji's colleagues to kill the boy instead. The Devil also seems overjoyed by the fact that it would be the one to kill the Chainsaw Devil.

When Denji finally decides to face it head on, Eternity screams about how the Chainsaw Devil was still alive after all, and that Denji is far weaker than how Pochita was in the past. After Denji kills it, Himeno later ponders to Aki why the Eternity devil talked like he knew about Denji.

Bomb Girl arc
After Makima tells Denji that she will have to borrow Power for an blood extraction, she introduces him to Beam, a shark fiend obsessed with Denji's chainsaw's powers. Denji then asks Makima why Beam has such devotion to him, which she responds by saying that Denji resembles someone, implied to be Pochita in the past.

Later, when Reze and Typhoon are laying waste on the city, Angel realizes that Beam knows about the original Chainsaw Devil and asks him to spit out any information about on him to help Denji better understand his powers.

Beam then claims that the Chainsaw Devil of the past was very fast, but he moved without having to walk, as he used the chainsaw chains to hook into things to swing between structures. Denji misinterprets this information, using his chains to hook Beam and mount him instead.

International Assassins arc
Due to Reze and Denji's fight being caught on TV, various countries began sending assassins to Japan in order to prevent Makima from having the Chainsaw Devil's heart, forcing her to cancel her travel with Denji and putting him into a 24 hours watch. Disappointed, Denji begins wondering who exactly Pochita is to begin with, and why everyone wanted his heart.

Gun Devil arc
Due to being unable to protect Denji and Power in Hell, Aki became distressed about the possibility of both of them dying in the upcoming operation to defeat the Gun Devil. Aki then asks Kishibe to quit the operation along with Denji and Power, surprising Kishibe, who expected Aki to be the one most eager for the event. However, Makima later persuades Aki to continue in the operation by forcing Denji and Power into staying with her.

Later, the Future Devil sends an ominous vision to Aki, stating that both him and Power will end up being slaughtered by Denji, and then the Devil that Devils fear the most will appear, foreshadowing Pochita's return in the future when Makima breaks his contract with Denji.

Control Devil arc
The Future Devil's prediction eventually comes true, Denji is forced to kill Aki and is unable to prevent Power's death by Makima. Left in a crippling depressive state, he asks Makima if it was all dream, unable to comprehend why she would do all of that. Makima then reveals that she wanted to bring Pochita back since the very beginning, however she was unable to do so because Pochita had to stay as Denji's heart due to the contract between them. Left with no other choice, she planned a way to break Denji's contract.

The terms of the contract stated that Pochita would remain as Denji's heart as long as Denji fulfilled his dreams of living a normal life. Thus, Makima made Denji live with Aki and Power in hopes that they would become like a family to Denji, and once that was done she would kill both of them to make Denji emotionally weak. Finally, she reveals that Denji killed his own father and manipulates him into believing that he was a horrible person because of his patricide and therefore did not deserve to live his dream of having a normal life. Denji agrees with her, and with that, Makima successfully breaks Denji's contract with Pochita, leaving the boy into an unresponsive state.

The day after, Makima walks alongside a catatonic Denji in a hallway filled with all of Tokyo's Special Division 4 Devils and Fiends. Makima then reveals that every single one of them were followers of the original Chainsaw Devil in hell, and that they were all waiting for his "resurrection". An unexpected explosion shows that Kishibe has brought in an entire division to kill Makima, with his agents then beginning to summon the Hell Devil to send her back to hell. However, she suddenly enlists the help of Chainsaw Man, forcing Pochita to take over Denji's catatonic body due to the broken contract, marking the fateful return of the original Chainsaw Man. Pochita quickly disposes of the Hell Devil, but the remaining agents revive it with blood and then it proceeds to cast Pochita back into hell. Soon after after arriving there, Pochita is greeted by hordes of devils that attack him. However they are no match for the original Chainsaw Man, as he quickly defeats them one by one effortlessly. Meanwhile, Makima reveals to Kishibe that Pochita is able to erase a devil's existence and the concept they represent by eating them, and that she's planning to fight him in order to defeat and control his power with the aim of erasing concepts that she deems unnecessary for humankind. Kishibe then asks her if she's not afraid of losing, which she responds by saying that she wouldn't mind being devoured by Pochita as she is a big fan of his.

Pochita somehow manages to find a way out of hell and returns to earth. Makima then reveals to Kishibe that Pochita will always aid those who ask for his help, but in return he will also kill them after the deed is done. Therefore, since she asked for his aid, Pochita is coming to murder her. She warns Kishibe to stay away and prepares to engage Pochita, but he kills her before she could even react. After briefly looking at Kishibe, Pochita hears Kobeni's call for help from far away and runs to her location, leaving Kishibe alone with Makima's remains.

Pochita goes to the burger restaurant where Kobeni is working. He looms over the staff and greets Kobeni with a "Vah!" A customer attempts to flee but gets instantly decapitated by Pochita. Pochita looks at the restaurant's menu and remembers a past request from Denji about how he wanted to try hamburgers. Sitting at a nearby table, he attempts to order a hamburger, speaking through a series of chainsaw revs. Suddenly deciphering Pochita's revs, Kobeni and the other employees prepare his orders as they sing and dance, with utter panic on all their faces. Pochita moves his arms, shuffling in time with their dancing. Kobeni is ordered to deliver the food to his table, but she trips and spills the food all over him. The staff try again, but Kobeni once again trips and spills the food.

Kobeni starts to cry while her boss begins to believe that the situation is an elaborate televised prank. Instantly, he is decapitated, and Kobeni begins to pick the ingredients up off the floor and reconstruct the burger. Pochita takes a bite, then remembers another past wish of Denji's- to go on a date with a girl- prompting him to grab Kobeni and carry her outside.

Stopping at an ice cream van, Pochita shreds it to pieces before acquiring a pair of ice creams for the two of them. As Pochita finds a Dance-Dance Mushroom machine, a Devil Hunter appears and threatens him but gets instantly eviscerated. Pochita drops Kobeni at the machine and orders her to dance. After commenting she has no money, Chainsaw Man shreds an ATM as Kobeni begins to play out of fear. As she continues dancing, Pochita leaves. He arrives on a rooftop, where he notices Makima nearby. Makima commands her allies, seven Human-Devil Hybrids, to emerge. They wager a date with Makima for the killing of Chainsaw Man, which Makima agrees to do.

Makima explains to Pochita the nature of her Hybrids and Pochita's last battle in Hell Weapon Devils and The Four Horsemen before disappearing. Pochita yawns at all this, and Makima orders her agents to attack him. Each agent transforms into their hybrid form and lunges at Pochita. As each makes contact with him, they get blown back by the force of him leaping forward, crashing through skyscrapers while slicing through Quanxi and the Broadsword/Longsword Hybrid. As they land in an apartment complex, Pochita kneels over the tattered bodies, clutching their severed heads. Behind him, Katana Man appears, attempting to slice through Pochita. He is unsuccessful, as it is shown Pochita was able to decapitate him without taking any damage himself. Makima looks on, calmly exclaiming that the conflict appears 'Unwinnable.'

Standing on the floor below Pochita, the Flamethrower and Whip Hybrid each attack him until Reze blasts through the building to grab Pochita, carrying him into the sky. Flipping midair, Pochita decapitates Reze but gets impaled by a spear thrown by the Spear Hybrid. While Pochita is stunned in midair, Makima blasts at him, repeatedly pointing at him and stating 'Bang,' each hit launching him further into the sky. Pochita is pushed out of the atmosphere and into space. Reaching inside his body, Pochita rips out his own heart and flings it towards the ground. As the heart begins to burn up upon re-entry to the atmosphere, Pochita's body reforms. While still falling, Pochita launches out his chains across the city, grappling Makima and the Whip, Flamethrower, and Spear hybrids. Hoisting them into the air, Pochita proceeds to tear them in half.

Pochita returns to Kobeni, sitting across from the girl as she finishes dancing. Suddenly, Makima reappears and asks Pochita why, despite killing her 26 times, he will not eat her. After taking the body of the Devil Hunter that Pochita had killed earlier, Makima tells Kobeni her fear of Chainsaw Man has weakened. As she says this, Pochita's body collapses onto the walkway, with blood beginning to leak from it. Due to Denji's heroic deeds as Chainsaw Man, the people's perspective of Chainsaw Man has changed from fear to adoration, weakening Pochita's powers as a result. Makima then reveals a powerful weapon using Angel's ability, intending to harm Kobeni. Pochita moves in front of Kobeni, pushing her away as the spear pierces through his torso. More blood gushes from Pochita's body, and his guts fall out as he collapses face-first onto the ground in a pile of blood.

Using the blood that Power made Denji drink from her, Pochita reawakens Power. He asks her to eat his flesh and revive as a Devil to help save Denji, and Power accepts. The revived Power emerges from Pochita's mouth in her Devil Form, and attempts to escape Makima with Pochita's body. Makima attacks Power and orders her to give Chainsaw Man to her, threatening to kill her for good. Power obliges, moving behind Pochita and lifting him up before stating that she had captured him. Pochita is shown in a state of shock and confusion as Power happily proclaims that the glory is all hers.

Makima orders Power to put Pochita's body down on the ground, but she runs away with Pochita, barely managing to hide themselves in a dumpster. From there, Denji and Power make a contract using her blood, allowing Denji to restore to his normal hybrid form while Pochita reverts back to his heart form.