Horada was a member of the Blue Squares gang and later the Yellow Scarves who served as a major antagonist in the first season of Durarara!!.
He was one of the members of the Blue Squares who, after being given information on her whereabouts by Izaya Orihara, captured and kidnapped Saki, the girlfriend of the leader of the Yellow Scarves Masaomi Kida. While Blue Squares gang leader Ram Izumii and his men (including Horada) held her in their van, Horada intentionally broke her leg to provoke Masaomi, presumably intending on killing him. However, the plan was thwarted by members of his own gang Kyohei Kadota, Walker Yumasaki, Erika Karisawa, and Saburo Togusa turned on them and rescued Saki.
Ram and the other men involved were arrested, but Horada escaped justice, and ironically later joined the Yellow Scarves. He was a member for around a year when he and his contemporaries decided to contact Masaomi and invite him to return to lead the gang, following intensive stress building between the Yellow Scarves and the Dollars, as catalysed by the mysterious Slasher, who Horada and many other members believed to be working for the Dollars.
Horada quickly became infuriated by Masaomi's passive approach to the conflict, and repeatedly ignored Masaomi, instigating many acts of violence against members of the Dollars. When members of his various teams came under the mind control of Anri Sonohara and attacked the other team members, Horada recommended that they be disciplined, but instead Masaomi kicked him in the head for his insubordination and came to the horrifying conclusion that his friend Anri was brainwashing members of his gang with a supernatural power.
As Horada's hatred of Masaomi grew, he decided to overthrow him as the leader of the Yellow Scarves by inciting an uprising while Masaomi was absent and having his men beat up and expel any members who opposed his leadership, blaming the attacks on the Dollars. He then personally shot the superhumanly strong Dollars member Shizuo Heiwajima in the leg and stomach, before claiming that Masaomi Kida ordered the hit.
After receiving word from Namie Yagiri that Mikado Ryuugamine, Masaomi's best friend, was secretly a member of the dollars, Horada taunted Masaomi by phone, saying that he would have the Yellow Scarves kill Mikado. To protect Mikado and Anri, Masaomi came to the Yellow Scarves headquarters in spite of his deposition by Horada, and confronted Horada with the intention of killing him. Masaomi easily defeated several of the men whom Horada ordered to kill him, prompting Horada to throw a crow-bar at his head, causing him to bleed profusely. He then pointed a gun to Masaomi's head, but Masaomi just continued to walk toward him. Horada made the mistake of revealing to Masaomi that he was involved with what happened to Saki, and that he was the one who broke her leg, furthering Masaomi's rage and drive to kill him.
Soon after, their confrontation was abruptly halted by the arrival of Anri, followed closely by the arrival of Mikado and Celty (the Headless Rider, a Dulahan fairy with darkness-based magic who can wield a supernatural scythe), who confronted the gang.
All of a sudden, it was revealed that around half of the members of the Yellow Scarves in the room were actually disguised members of the dollars, lead by Katoda, who attacked the Scarves from the inside in an all-out battle, during which Masaomi collapsed as a result of his head injury, and Katoda took him to the hospital.
In an act of self-preservation, Horada and three of his lieutenants fled the scene of the battle, and drove away in their car, only to be pursued by Celty on her motorcycle. While ahead of Celty, they encounter Shizuo who has recovered remarkably well after being shot, and who used a traffic sign to slice the top off of the fast-moving car in an attempt to kill Horada in vengeance for shooting him. The attempt failed, so Shizuo threw the signpost at the car, where it collided with the bonnet, causing small explosions to spout from the engine.
Celty continued to pursue Horada until he passed a motorcycle police division led by officer Kinnosuke Kuzuhara, who arrested him for dangerous driving. Horada attempted to file charges against Shizuo for damaging his car, but failed.