Aki Hayakawa

While Denji and Power are out on patrol, Aki drives Makima from her meeting with her superiors. In the car, Makima explains to Aki the reason she is intrigued by Denji at the moment is due to his ability to transform into Chainsaw Man. While struggling to handle Power’s chaotic demeanor, Denji recalls they were put together by Aki's recommendation. This causes Denji to become furious, believing that Aki is purposely trying to get him fired. During the aftermath of the Bat Devil's defeat, Aki and his squad arrive just as Denji is about to be devoured by the Leech Devil after being impaled by her tongue. Aki saves Denji by summoning the Fox Devil, who quickly emerges to swallow the Leech Devil whole. Once the Leech Devil is handled, Aki gives out orders to his teammates while escorting Denji to the hospital.[11]

Once Denji recovers in his hospital bed, Aki explains that Devil Hunters are able to form contracts with Devils by giving parts of their body away in exchange for helping them fight. Aki also reveals why he can use the Fox Devil by revealing that he gave part of his skin away. Though, Aki expresses disdain towards Devils, claiming they can't be trusted, and threatens to report Power and Denji should they not obey his orders as their superior.

On Denji's first day as a Public Safety Devil Hunter, Makima introduces Aki as his senior and tells him to work with Hayakawa for that day. While patrolling the city, Aki slowly becomes annoyed with Denji asking whether Makima has a boyfriend. This leads to Aki pushing Denji into an alley to beat him up, as a warning that if he doesn't take Devil Hunting seriously, he could end up dead. Aki bluntly warns Denji to leave for his own good before turning to leave.In an unexpected moment, Aki is repeatedly struck in the groin from behind by Denji, who states that he would risk his life to continue living the way Makima had shown him. Aki proceeds to slug Denji in return and tells him Makima would never have interest in a thug like him before collapsing from being kicked in the groin too many times. Once they return to the Public Safety Headquarters, Makima assigns Denji to Special Division 4 while arranging him to live with Aki in his household. Although reluctant at first, Aki takes care of Denji despite feeling annoyed towards his new coworker's carefree way of living. One day, the two go on a mission to hunt a down Fiend. After witnessing Denji kill the Fiend by beheading it, Aki questions him why he didn't transform to finish the job. Aki lectures him to not show Devils any form of sympathy, as his own family was killed by one. Denji explains his reasons, including wanting to make friends with one as he doesn't have any friends. Shocked, Aki leaves not before telling Denji he'll remember his reasons. Aki is later present when Makima introduces Denji to his new buddy: the Blood Fiend Power.

During his childhood, Aki lived with his parents and younger brother Taiyo Hayakawa. On November 18th, everything changed when the Gun Devil appeared during an American terrorist attack involving guns. While waiting for Taiyo to fetch his gloves so they can play a snowball fight, Aki witnessed his family getting brutally killed in the crossfire. With his life changed forever, Aki would swore vengeance on the Gun Devil for killing his loved ones. As he grew older, Aki joined Public Safety with a strong desire to finish off the Gun Devil. It was at this point where Aki would be partnered with Himeno after being introduced to her at a graveyard by Kishibe. He learns that Himeno had recently lost her fifth partner, and is told to not die like the others have. From that point on, Aki and Himeno would work together on several missions while forging a strong bond as the two became buddies over time. Himeno taught Aki how to smoke, made him pierce his earrings, as well as trying to convince him to leave Public Safety for his own safety. He would also work under Division 2 before being transferred to Special Division 4. Unbeknownst to Aki, the Gun Devil was already defeated a long time ago and was separated into different segments across different countries.Regardless, Aki continued working under Public Safety as long as it got him closer to killing the Gun Devil when the time had come.

Hokkaido, Japan

1,82cm (6'0)

Male

Curse Devil Contract: Aki had a contract with the Curse Devil which granted him a nail-like sword. In order for the contract to work properly, Aki must point the nail anywhere on his target's body; then saying the word "fire", the hand of the Curse Devil will appear and flicks the back end of the nail to inflict damage. By stabbing his enemy three times with the nail, Aki could summon the Curse Devil to seize the enemy and inflict massive damage upon them, potentially killing them in the process. In order to use it, Aki's life would be significantly shortened.

Fox Devil Contract: Aki originally had a contract with the Fox Devil. In exchange for feeding him part of his body, Aki could use his power in combat by raising a hand and saying the word "Kon" (コン, "Kon"?), causing the Fox Devil's head to appear to instantly bite down on the target's body, swallowing him whole or tearing him apart. Aki lost the ability to summon her after he used the Fox Devil recklessly against the Katana Man.[3] Future Devil Contract: After losing favor with the Fox Devil, Aki was taken to the Future Devil that is held prisoner by Public Safety and managed to gain a contract to use its abilities in exchange for letting the Future Devil live inside his right eye. Precognition: Aki had the ability to see a few seconds into the future. He used this to predict his opponent's oncoming attacks and plan accordingly. Summoning: Due to his contract, Aki could summon Future Devil by calling him. While the Devil says that Aki must say "The Future Rules" to make him come, this was not an actual requirement. Control Devil Contract: Aki made a contract with the Control Devil, in exchange for his entire being he gained her power, however, as he was completely under her control, he was unable to use it.

Aki generally appeared to be a very stoic man who acted mature and sometimes blunt to the point of rudeness when he was with his fellow Devil Hunters, but he was actually fairly softhearted. He had a tendency to get attached to others easily, and hated to see people get hurt, especially his close friends. Unlike many of his associates, he was described by Himeno as being a "normal person", in the sense that he still grieved for those lost and had not become jaded enough to close his feelings off. Despite this, he was very determined and his primary motivation for killing the Gun Devil was revenge for his family. However, he was entirely willing to put his own life on the line to save other people, even if it got in the way of his goals.

He didn't like people who don’t take their job as Devil Hunters seriously or fight for a superficial and materialistic goal like money or, in Denji's case, to be able to touch some boobs, this being one the primary reasons he and Denji didn't get along initially. Aki was also ruthless, stating that he always makes sure the Devils he kills suffer in order to give them a slow and painful death. He could become intimidating with those he still didn't trust enough, like when he threatened Denji by telling him that if he either betrays them or sides with other Devils, he would kill him without any hesitation. Despite being merciless, Aki still had some kindness with his fellow devil hunters, such as retrieving Denji's severed arm, taking Meowy to get medical attention, freeing Power and intentionally lying in his report to Makima in order to uncover the truth of the incident with the Bat Devil.

His air of cold detachment was a façade as he had been seen to cry over the deaths of his comrades such as Himeno and he grew to care for Denji and Power enough to try and forfeit his revenge goal in order to keep them safe.

Aki also was capable of being afraid to lose those he deeply cared about.

Aki was a handsome, tall young man with medium-length black hair that he usually wore in a topknot style (shoulder-length with long bangs when untied) and blue eyes. In the past when he and Himeno met through Kishibe and became partners, Aki used to have shorter hair.

He often wore the Public Safety Devil Hunter uniform; a suit and tie. He also donned black earrings and usually carried his sword on his back.

Hayakawa Aki