Denji/History

Intro arc
At the start of the series, Denji is forced to do odd jobs and kill Devils for the yakuza to pay off the debt from his late mother's medical expenses that his father did not pay off before taking his own life. His best friend is a Devil dog named Pochita, whom Denji saved by giving the wounded demon some of his blood to heal, unintentionally forming a contract with him. When the yakuza betrays Denji and sacrifices him to the Zombie Devil, Pochita becomes Denji's heart and revives him as the Chainsaw Devil. Denji then defeats the Zombie Devil and a portion of his zombie army.

Afterward, he meets Makima, who forces him to join the Public Safety Devil Hunters and threatens to exterminate him as a Devil if he ever refuses her orders. After killing the Muscle Devil, Denji becomes a sanctioned Devil Hunter and begins working with Aki Hayakawa and the fiend Power.

Bat Devil arc
Under the promise that Power will let him touch her chest, Denji is tricked into becoming a sacrifice for the Bat Devil in exchange for her cat. After the Bat Devil eats Power, Denji chases after the Devil and defeats him. The Leech Devil then appears and overwhelms Denji, but he is saved by Aki and the Fox Devil. Afterward, Power moves in with Denji and Aki, and she lets Denji get to second base as a reward for saving her cat.

As Denji's joy of the experience slowly turns to melancholy, Makima tells him that if he can manage to kill the Gun Devil, she will grant any wish for him. To find the Gun Devil, the Public Safety Division has to collect pieces of the Gun Devil's flesh granted to other Devils.

Eternity Devil arc
Seeking a piece of the Gun Devil at a hotel, Tokyo Special Division 4 is trapped in a moment of time by the Eternity Devil, who demands Denji's heart in exchange for freedom. The Division 4 members begin to turn on Denji to ensure their escape, but Aki defends him. Denji drops into the Eternity Devil's mouth and fights it for three days straight, eventually finding its weak point and destroying it, freeing everyone.

During the victory celebration, fellow Devil Hunter Himeno comes onto Denji before throwing up in his mouth during his first kiss and then offers to sleep with him. Denji refuses, wanting to save himself for Makima, and he and Himeno become friends afterward.

Katana Man arc
Denji and his team get ambushed by the Katana Man and Akane Sawatari, and Himeno is killed. Denji is defeated by the pair and only manages to avoid capture thanks to the combined efforts of Makima and fellow Devil Hunter Kobeni Higashiyama.

The strongest Devil Hunter in the Public Safety organization, Kishibe, trains Denji and Power in preparation for an attack on the yakuza group that attacked the Public Safety Devil Hunters. Denji has his rematch with Katana Man and wins. Joined by Aki, Denji holds a nut-kicking tournament to see who can get Katana Man to scream the loudest as payback for Himeno.

Bomb Girl arc
While out on patrol, Denji escapes from the rain in a nearby phone booth and encounters a girl named Reze. After a short conversation, Reze invites him to the café where she works and gives him a cup of coffee. Denji starts to develop feelings for Reze and begins visiting the café regularly. Through their conversations, Reze learns that Denji has never attended school and offers to break into a local school with him. Afterward, Reze invites Denji to a local festival, and they share a kiss during the fireworks display. During the kiss, she bites his tongue off and reveals that she is a Bomb Devil hybrid. The Shark Fiend, Beam, rescues Denji and the two escape to the Second Division headquarters.

Denji and Beam are assisted by Aki, Angel, and the Second Division for a short time but are ultimately forced out by Reze's attacks. The Typhoon Devil joins the fray, and after a lengthy battle, Denji defeats Reze, using his chains to restrain her. Thinking she will not be able to use her powers underwater, he throws themselves into the ocean. Later, the two wake up on the beach, rescued by a now-unconscious Beam. After a short conversation, Denji asks Reze to run away with him and if her feelings for him were genuine. She rejects him and turns down his offer to run away. Denji lets her leave but tells her that he will wait for her at the café. With a backpack and an envelope of money, Denji waits at the café with a bouquet for Reze, but she never comes.

International Assassins arc
The fight with Reze has revealed Chainsaw Man to the world, and assassins from around the globe hunt down Denji and his heart. Together with Devil Hunters from Public Safety, Special Division 4 works to protect Denji from his assassins, one of them including Quanxi, the First Devil Hunter and the Crossbow Devil hybrid. During the all-out battle, the Hunters get sent to Hell and encounter the Darkness Devil. Denji attempts to fight the Devil but is quickly incapacitated. They are rescued by Makima, who revitalizes Denji and has him defeat Santa Claus.

Gun Devil arc
Special Division 4 recovers from their encounter in Hell, with Aki and Denji taking care of a now-traumatized Power. Makima invites Denji to go on a trip with just the two of them, but he turns her down to help Power. During this time, Denji concludes that there are some things he is better off not knowing, dismissing the mysterious door in his dreams. Afterward, Special Division 4 learn the truth about the Gun Devil from Makima and that they are to take a piece of its body from another country into Japan's possession. When the Gun Devil attacks Japan to kill Makima as ordered by the U.S., Denji and Power are attacked at home by Aki, who has transformed into the Gun Fiend. With no other choice but to stop him at the pleas of the innocents, Denji kills Aki, which greatly disturbs him.

Control Devil arc
With Denji at his lowest, Makima shows her true colors as the Control Devil, killing Power and revealing her true intentions to Denji: to break his contract with Pochita and gain access to Chainsaw Man and his ability. Makima proceeds to break Denji's psyche, leaving him in a catatonic state. Pochita takes control of his body and tries to restore their contract. With the help of a revived Power, Denji is brought back and hides away with Kishibe and Kobeni. Watching the television showing the positive reception to Chainsaw Man, Denji expresses his selfish dreams for his life and desire to keep being Chainsaw Man. Plotting with Kishibe, Denji confronts Makima for the final time and is able to defeat her. Despite everything Makima did to him, Denji still likes her, and to stop her from reviving, he commits to cannibalism and eats Makima's body.

Denji meets with Kishibe, who puts Nayuta, the reincarnated Control Devil, under his care. Later, Denji has a dream with Pochita, who tells him to grant the Control Devil's dream by forming an equal relationship with her as a family. Denji then leaves Public Safety and starts attending high school while continuing to be Chainsaw Man.

Justice Devil arc
Battling the Cockroach Devil, Denji inadvertently saves Asa Mitaka and Yuko, once again killing the Bat Devil in the crossfire. Killing the Cockroach Devil, he is acclaimed by the news for saving a cat.

Still wishing to get a girlfriend, Denji makes several attempts to expose his identity, but to no avail, as Hirofumi Yoshida protects his identity under a secret mission. He later meets Asa, who rejects his claims of being Chainsaw Man. Denji later battles and beats Devil Yuko in a one-sided fight.

Dating Denji arc
Denji gets invited on a date with Asa to the aquarium, unaware of her plan to turn him into a weapon. The Eternity Devil returns from Hell and traps both of them, along with several members of the Devil Hunter's club, via Fami's scheme to force Asa to turn him into a weapon.

While trying to find a way out, Denji tells Asa more about himself, and the two bond as she devises an escape plan. After gathering over one million yen, Asa tells Denji to give her the money, promising to grant any request after they escape, and Denji agrees. Everyone is freed from the aquarium after Asa changes it to a spear and defeats the Devil. Denji walks Asa home and asks her on a second date, which she agrees to do. Suddenly, Yoru possesses Asa, puts her hand on Denji's head, and calls out: "Denji Spinal Cord Sword."

Denji is confused and interprets this as a farewell, mimicking her before leaving. The next day, Denji meets up with Asa after school and tells her his date plan: watching a non-stop movie marathon at the theater. Asa complains about the price, and they agree to have the movie date at Denji's home. Denji reluctantly accepts under the condition that Asa follows the home's rules because, in the worst-case scenario, she could die if she breaks them.

Denji takes Asa to his apartment, where he explains the home's rules to her. As they watch the movie together, Denji tells Asa not to make out with him in front of his roommate, which gets Asa flustered, and she says she has no desire to kiss him and actually hates him. After Asa pushes Denji away, Yoru takes over her body and kisses him. Nayuta comes home from walking the dogs and calls Yoru a thief, linking a chain from her finger through Yoru's skull and turning her into a dog.

Denji tells Nayuta to turn "Asa" back immediately, but Nayuta asks Denji if he is sure he wants that, reminding him that every woman he meets tries to kill him and asks what makes her any different. After some thought, Denji states that it is a feeling. Nayuta agrees to turn back Asa but on two conditions: allow her to eat ice cream every day and not make friends with Asa anymore, wary of Asa's bad scent. Denji is conflicted but decides to put Nayuta first, and she alters Asa's memories to make her believe that Denji stood her up.

Current arc
At night, Nayuta smells a "nasty devil scent" and insists that Denji go hunt it. However, Denji is depressed and does not want to be Chainsaw Man anymore, saying that Nayuta will only block him from more future ladies. Nayuta motivates Denji by telling him that as Chainsaw Man, he could get more love from people than a girlfriend.

Denji locates the Falling Devil, and they begin to fight. The Falling Devil recognizes that he is Chainsaw Man and requests a ceasefire, explaining that her job is to drop Asa into Hell to feed its residents. Wanting to protect Asa, Denji sees even more of a reason to kill the Devil. The Falling Devil uses her ability to make Denji remember his loss of Aki and Power, floating him into the air.

Denji cuts up his brain to resist the mental attack and drops down to continue fighting the Falling Devil. Craving corn dogs, Denji devours the Falling Devil, who regenerates with a blast, tearing Denji apart from the waist down. After the Devil leaves to search for Asa, an unknown individual approaches the defeated Denji and cuts their hand, using their blood to revitalize Chainsaw Man, saying that he is still needed to fight.

The restored Denji follows after the Falling Devil, who has already captured Asa and made her fall. Still in his hybrid form, Denji quickly jumps over to Asa, grabbing her and holding on to a nearby railing. To his confusion, they continue to fall upward as Asa pours out her negative views on life. Denji realizes the Devil's ability and tells Asa to think happy thoughts, managing to stop themselves in midair. Denji tells Asa that he knows how she feels as he has experienced similar things. Asa asks how he is able to overcome all the bad things in life, and Denji states he has something to live for that keeps him going: to have sex, and Asa reacts with disgust.

Asa and Denji proceed to argue about sex, and Asa tells him that no one would want to have sex with him. This puts Denji in despair, and the two fly up through a door to Hell. Denji finds himself and Asa on the Falling Devil's prepared dish and rushes back to the door, quickly regenerating himself when he gets attacked by a Devil. Denji finds, however, the Falling Devil on the other side of the door, preventing him from leaving. Denji is then surprised when the Faliing Devil is slashed up by a Chainsaw Man doppelganger, who tells him to avoid the devils seeking to devour Asa until sunrise.