Keigo was born on the island Kyushu, Fukuoka. The floor of what's assumed to be Keigo's childhood home was shown to be littered with garbage, broken shards and alcohol bottles, and Keigo himself was portrayed as an expressionless, quiet child. When he was a child, he was saved by Endeavor, which caused Keigo to admire him. It is likely because of this that he got an Endeavor doll.
At some point during his childhood, Keigo saved the lives of many people from a high-speed car accident. The public was shocked to discover the savior was a young child and the hero public safety commission decided to train him as a hero. It was stated that the commission drilled interpersonal skills into him from a young age, so he could master the art of deception and infiltration. The commission forced him to abandon his real name and made him undergo years of hard training, which he accepted in order to be a hero like his idol Endeavor.
Reaching 18 years of age, Keigo started his own hero agency and by the second half of that year, he ranked in the top 10 of the Hero Billboard Chart JP and became the youngest and fastest hero to ever have done so. Four years later Keigo reached the No. 3 Pro Hero rank, behind only All Might and Endeavor, without even trying. Unlike many heroes, Keigo was never interested in being the strongest or being like All Might; instead, he admired Endeavor.
During the rise of the League of Villains, Keigo took on Fumikage Tokoyami as an intern at his office. Keigo wanted to gain more information about the villain group, and so decided to pick Fumikage because he placed 3rd at the U.A. Sports Festival and because they're both bird-like humanoids. However, during his internship, Keigo fought crime too fast for Fumikage to keep up with, and, when talking to him, only showed interest in information about the League.
Fumikage returned to Keigo's side for his Hero Work-Study. This time, Fumikage tried again to keep up with Keigo using new techniques, and, impressed, Keigo took his protege for a flight over the city as a reward. He commended Fumikage for compensating for his weakness but advised him to improve on his strengths as well. Keigo believed that Fumikage had wings and didn't need to be confined to the ground. Keigo's "Be free like a bird"-tutelage allowed Fumikage to develop his Black Fallen Angel Super Move.
After the attack in Kamino, Yokohama, the Hero Public Safety Commission approached Keigo with the command that he had to become a double agent to infiltrate the League of Villains. Keigo had no chance to refuse the order. 
In November, Keigo is present in the second half of the year's Hero Billboard Chart JP. During the event, it is announced that Keigo rises up one rank to No. 2 in the Top 10 hero ranking. Disinterested in the speeches of the other Heroes, Keigo interrupts Edgeshot and takes the microphone. Keigo flies above the podium and gives a speech about how the approval rating system is the most important of all and how he disdains the speeches of the other heroes. Keigo flies down and hands the microphone over to Endeavor. After Endeavor's assuring statement, Keigo applauds him.
Backstage in Endeavor's room, Keigo is talking to a displeased Endeavor, since he enraged him during the event. Keigo explains that he tried to help Endeavor on the podium as he sees that Endeavor is fit to be a new leader to support everyone after All Might's retirement and expresses that he sees himself not fit to have that role, preferring to be in the lower ranks. Before Endeavor leaves dissatisfied with him, he requests Endeavor for a team-up as there has been an increase in concerning sightings in his area, reminding Endeavor about the Nomus, to the Flame Hero's shock.
Keigo brings Endeavor to Kyushu where he decides where they will eat to discuss the proposal of working together. During their trip, Keigo effortlessly takes out an extreme follower, helps civilians and socializes with his fans. Keigo decides to eat with Endeavor at the Umai building, where Keigo tells Endeavor about the appearing rumors of the Nomus around the country instilling fear in the civilians and asks Endeavor, as the No. 1 hero, to reassure them. After getting the check, they are attacked by the rumored Nomu. Keigo is tasked by Endeavor to evacuate the building while he battles the creature.
Meanwhile, Endeavor is facing off against High-End. Keigo is surprised that Endeavor can fly to which Endeavor considers it "not falling" and warns him not to underestimate the Nomu they are facing. High-End starts regenerating and comments on Endeavor's foolish attempt to finish it off in one strike.
High-End smashes Endeavor across the building, so the top half of the building begins collapsing. Keigo uses his feathers to get all the injured civilians out of the building first. As Keigo's feathers begin delivering the injured down to safety, Keigo himself joins the fight and launches three feathers, which successfully strike its arm. Endeavor uses an advanced version of Flashfire Fist: Hell Spider and strikes High End with multiple fire streams that cut up its body. Keigo wonders if this move is his strongest, to which Endeavor comments about it not even being close. The cut-up High-End begins regenerating, and comments on the fight being interesting.
Endeavor continues his battle with High-End and uses his fire streams to cut up the collapsing top half of the building. Keigo assists with cutting up the top half with his feathers and they manage to stop the building from collapsing. High-End continues regenerating but is hit by one of the Pro Heroes on the ground. Annoyed, High-End releases and sends several white Nomu to attack the Pro Heroes and civilians. Keigo uses his feathers as blades and cuts through two white Nomu, saving civilians in the process.
After High-End survives Endeavor's strongest attack, Keigo shouts a warning to the Flame Hero, but High-End strikes Endeavor, impaling his torso and striking him in the face, injuring his left eye.
On the ground, Keigo deals with the rampaging Nomu as the security forces take them into custody. Keigo notes to himself that he was fortunate they weren't too strong before he was alerted of the destruction caused by Endeavor and High-End. Keigo later makes it to the fight where he uses his feathers to enhance Endeavor's speed, allowing Endeavor to be launched at the villain. Keigo reminisces that he always watched the latter struggle to surpass All Might and voiced his desire to help Endeavor in his task.
As Endeavor attacks High End, the impact of his attack blows Keigo away and he is surprised by the speed. Endeavor screams for Keigo to give him more speed to help, Keigo complies but points out that his feathers are now practically ash. Endeavor states it is more than enough and uses it to send him and the Nomu far from the city. With nothing to stand his way, Endeavor uses a finishing move while shouting 'Plus Ultra' noting he always hated his old school's motto, to destroy High End for good. Endeavor emerges from the destruction and strikes a pose, similar to All Might's to show he is victorious. Keigo comes to his aid and the two share banter about the pose before moving to get help for Endeavor's wounds. However, they don't get very far as Dabi appears on the scene and Hawks is confused by the latter's familiarity with Endeavor.
Later on, Keigo meets with Dabi in an alley, they discuss their initial plan and Keigo is angry that Dabi didn't keep to it but he tells Keigo he couldn't trust him right off the bat as he might be using him. Dabi brings up Hawks bringing Endeavor when it should have been a random hero and questioned the lack of casualties. Keigo tells him he had to keep up appearances, Dabi understands but tells him he won't be seeing the boss but promises to contact Keigo again. While walking, Keigo recalls his mission assigned to him by the Hero Public Safety Commission of gaining the League of Villains' trust and feels guilt at Endeavor's condition as he visits the latter at the hospital.
After Endeavor is discharged from the hospital, Keigo walks with him to the airport showing guilt over the injuries that Endeavor has received. Despite Endeavor blaming the injuries on his own actions, he is suspicious over the timing of the Nomu attack, Keigo brushes this off by saying their high profile presence would have attracted attention. Keigo had deliberately set up their meeting to catch the public attention, to provide himself with an excuse for the attack. Endeavor warns Keigo to be careful in the continuance of his investigation, to which Keigo teases him for his consideration. He tells Endeavor it will take another day or so before all his feathers grow back and tell him to rest as well, as he sees Endeavor off.
Afterwards, Keigo thinks back to his meeting with the Hero Public Safety Commission in which he recalls their rather forced proposal to join the league. Despite Keigo's remarks, they tell him his absence from the Kamino incident was very fortunate for them. Thinking back to his childhood, Keigo had always been driven towards the path of heroism ever since he saved a group of people from a 130 km/h car accident. The word that a child saved the day was discovered and Keigo's family was supported on behalf of his upbringing as a hero. Flashing back to the commission, Keigo agrees to corrupt himself and take on the job, as long as it puts everyone else at ease. He fantasizes about his dream of a society in which heroes have more free time and vows to make it a reality as fast as possible.
While in Osaka, Keigo tries to contact Dabi to confirm their arranged meeting to no avail. Keigo suspects that something is wrong due to the League of Villains' unusual behavior. He flies off with a duffel bag and thinks back to a previous phone call he had with Dabi. Dabi gives Keigo one last unspecified job to prove himself to the League. Shortly afterwards, Keigo visits the Number 3 Hero, Best Jeanist. Best Jeanist welcomes the Number 2 Hero into his home and reveals that he had lost a lung during the Kamino incident and that he is planning to tell the public about it soon. Keigo responds how unfortunate things had turned out before unsheathing his feather sword. Back in the present, Best Jeanist is revealed to have gone missing as Keigo flies past a billboard. No one, including his sidekicks, has any knowledge of his whereabouts.
Keigo later made contact with Dabi and revealed that he is aware of the truth that League attacked Deika City. He also shows Dabi Best Jeanist's body, as the latter voices his approval despite being suspicious of the authenticity.
Keigo soon witnesses the alliance of the League and Meta Liberation Army, forming the Paranormal Liberation Front and considers the gravity of the situation. He realizes that he's too late and wishes the League had been dealt with sooner for the sake of the innocent civilians who were killed in the recent battle. Seeing their increased numbers and resources, Keigo deduces that with a committed army following; Feel Good Inc's network, Detnerat's industry influence and possibly more High-End Nomu, Tomura has gain power equal or greater to the Heroes. Later on, Keigo meets Dabi among the crowd. Keigo wonders about getting a few introductions while noting to himself that there is still an unknown backer that needs to be revealed before the Heroes can make a move.
After returning from a coffee run, Keigo is confronted by Slidin' Go for not notifying them and Keigo tells him that he had the freedom to do as he pleased, which is the organization's goal. Slidin' Go tells Keigo to comply since he was of higher rank only to back down when he is confronted by Skeptic. Skeptic reveals he put microdevices in Keigo's wings to monitor the Heroes' activities and that he also knows what Keigo himself has been doing. After things quell down, Keigo briefly recalls how he told his superiors of how their conversations will be monitored and have them communicate in code while he investigates the Nomu manufacturing location. While reading the Meta Liberation War book on a building, he notices Endeavor on the field against a Villain.
As Endeavor chases Starservant through an alley, Keigo swoops in to take out the minions who were about to ambush Endeavor and he happens to encounter Endeavor’s three interns. After the fight, Keigo briefly chats with Izuku and Katsuki before Endeavor asks him why he is here. Due to the listening devices in his wings, Keigo is unable to tell Endeavor anything directly about the growing threat, instead, he knowingly contradicts what he said back in Kyushu by saying positive things about the Meta Liberation Army and Destro's autobiography, in hopes that Endeavor will catch on.
Keigo proceeds to hand copies of Destro's autobiography to Endeavor’s interns and heads off. While flying back, he recalls how he highlighted certain parts in the book to pass onto Endeavor because he was being monitored. He returns to PLF base, to give his report to the lieutenants. After doing so, he uses his wings to spy on their future plans.
Hawks tricks the surveillance of the Paranormal Liberation Front, while still preserving his facades. He helps them, acts honest, reliable and devoted as he gathers various sensitive information about the inner secrets and structures of the organization without drawing suspicion. Then he received Oboro's "hospital" hint from his superior and combined it with the information that Tomura was in the mountain near Kyoto, to locate his target. Hawks concluded that, if the PLF made their first move, the heroes would lose.
So Hawks pulled his contacts to organize the hospital raid and the attack on the PLF headquarters, knowing he would risk his status. Once the raid starts, Hawks decides to make his move as fast as possible. He soon confronts Twice with two twin feather sword blades and corners him in the same learning room with several more floating feather blades.
Revealing himself as a double agent, Hawks explains his undercover actions to Twice: he had gotten the tracking devices out of his wings, and manipulated Twice because of how his Quirk, Double, was a huge threat. Hawks tells him that he plans to take him into custody once the war is over. This causes Jin to experience a mental breakdown, blaming himself for letting Hawks relay his information to the heroes, putting himself and all of his allies in danger. Hawks tells Twice that he wants to redeem him because he believes that he is a good person.
Angered by these words, Twice lashes out in rage and despair out of his hatred towards the heroes. He uses Infinite Doubles: Sad Man's Parade, proclaiming that he'd trade his soul for the League's happiness. Hawks sighs as he reluctantly agrees to fight the one he considered a good friend. As their battle continues, Hawks repeatedly counters Twice's attacks using his multiple feather blades to dissolve them to nothingness. Hawks also comments on the durability of Twice's Double Quirk, adding that he'd never let sentiment trip him up on an opportunity like this.The Winged Hero manages to subdue Twice with his quick speed, solemnly stating that if neither hero nor villain will give up, one of them has to die. With that said, Hawks prepares to finish off Twice, only to get blasted by a large blue flamethrower from another side of the room. Both Hawks and Twice are sent flying by the unexpected attack. A figure then steps on Hawks' face enveloping flames around his soles, revealing himself to be Dabi. Dabi reveals that he heard everything Hawks mentioned and taunts him for making excuses for his behavior. However, Hawks barely dodges Dabis' flames in time using one feather blade to carry him and Twice to safety.
Upon being told he has barely any feathers left, Hawks calls out Dabi for nearly burning his friend to death. Dabi sarcastically tells Hawks its expected of him to dive in and risk his life for others' safety. Hawks then learns that Dabi never considered trusting him from the start of their 'cooperation' and tries strategizing another plan to take down both villains at the right timing.
Before he could take action, Hawks loses his grip on Twice, much to his annoyance. Hawks manages to shrug off one of Twice's doubles before being blasted once again by Dabi's flames. Despite this, Hawks swiftly maneuvers away from Dabi's range and attempts to attack Twice. Dabi reveals that he knows Hawks' real name, surprising the hero in the process. Regardless, Hawks and Dabi continue to fight while Twice makes his escape. Unfortunately for Twice, Hawks appears and lands a fatal blow on the villain, reluctantly killing him in the process.Enraged, Dabi stomps on Hawks while ruthlessly burning him, scolding the hero for killing Twice. Hawks notices the psychotic grin on Dabi's face and asks him if he's making the face of someone who's seen a friend die. Dabi tells him that his tear glands are burned up and he is upset by Twice's death since he was necessary for his own dream to come true. Hawks asks Dabi whom he is, and is shocked when the villain reveals his real name to him. As Dabi explains that he never cared about the League of Villains as well as Hawks' life, he prepares to kill him with his flames. However, Hawks ends up being saved by his protege, Fumikage. Despite arriving on time, Fumikage realizes that Hawks' back is badly burned and all of his wings are nearly gone.
Dabi then cruelly points out that Hawks murdered Twice while the latter was trying to protect his friends, even adding that the Winged Hero is dirtier than any Villain. Fumikage refuses to falter and tries to carry Hawks to safety while holding back Dabi by using Dark Shadow to attack the villain. A barely conscious Hawks tells Fumikage that Dabi will keep talking as his taunting serves as a way for him to recharge his flames, telling his intern to leave. However, Fumikage fails to grip on one of the ledges while trying to escape. This results in both Heroes crashing down on concrete, which causes Hawks to go unconscious.
Noticing that his master is unconscious, Fumikage tries to use Black Fallen Angel but Dabi appears before them hovering. He prepares to blast them to ashes while noting he saw Hawks' betrayal coming. However, their skirmish is interrupted by Geten's sudden ice attack, allowing Fumikage and Hawks to escape from the battlefield. While fleeing, Fumikage tearfully tells the wounded Hawks that what he did wasn't wrong and it was the right thing to do.