At some point during his childhood, Keigo saved a family from a high-speed car accident. The family was shocked to discover their savior was a child and vowed to support him and his family.
At 18 years old, Keigo started a hero agency and by the second half of that year, he ranked in the top 10 of the Hero Billboard Chart JP, the youngest and fastest hero to ever do so. Four years later Keigo reached the No. 3 Pro Hero rank behind only All Might and Endeavor. Unlike many heroes, Keigo was never interested in being like All Might. Instead, he admired how Endeavor was the only one trying to surpass him.
During the rise of the League of Villains, Keigo takes on Fumikage Tokoyami as an intern at his office. Keigo wanted to gain more information about the criminal group and decided to pick Tokoyami because he placed 3rd at the U.A. Sports Festival and because they're both birds. During that week, Keigo fought crime too fast for Tokoyami and the other sidekicks to keep up.
Tokoyami returned to Keigo's side for his Hero Work-Study. This time Tokoyami does his best to keep up with Keigo using new techniques. Impressed, Keigo takes his protege for a flight over the city. He commends Fumikage for compensating for his weakness but advises 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 tutelage allowed Fumikage to develop his Black Fallen Angel super move.
Sometime after the attack in Kamino, Yokohama, the Hero Public Safety Commission approached Keigo with the request that he become a double agent to infiltrate the League of Villains and ensure they have no secretive way to escape if they are found.
In November, Keigo is present at 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 of 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 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 which cuts 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 his 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 tells 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 of 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 on 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 the 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 chased 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 Midoriya and Bakugo before Endeavor asks him why he is here. Stating because of the listening devices in his wings, Keigo is unable to tell Endeavor anything directly, instead he says positive things about the Paranormal Liberation Front and their book, seemingly in an effort to warn Endeavor that the PLF are a growing threat.
Keigo proceeds to hand books 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 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.