Season 1

Akira, the series protagonist, is a participant in a fighting tournament called "Bl@ster," after a successful battle, he retires to his quarters. He's awakened from sleep when a group of police break into his room and pin the blame for a recent murder on him, a crime which carries a sentence of life imprisonment. With no way to defend himself against the charges, Akira waits in fear for his life. He's visited in jail by a woman named Emma who offers him the only alternative to a life spent in captivity - join a higher-stakes fighting competition, and defeat the man at the top. Faced with no other option, Akira gathers his things and leaves for the city of Toshima, where the Igra competition is held. He has nothing more than the clothes on his back and the dog tags that peg him as a participant, so when some thugs show up to harass him and take a hit of a drug giving them super powers, he has little recourse. He's only saved by a man dressed in black, who brutally murders his attackers with his sword. The man threatens Akira as well, only letting him leave with his life when Akira shows too much pride to beg for his life.

After surviving his first day in Toshima, Akira is surprised when Keisuke turns up; he has followed him into the city. Not letting this change his mission they both set out into the city and are met by Rin who takes them to the Castle, the intake place for Igra.

After entering Igra, Keisuke is attacked by a mysterious blue haired boy who steals all of his tags. Akira stepping in defeats the stranger and reacquires the tags. Later on after losing an item belonging to his sister, the stranger grabs Akira and demands it back.

Rin finds Akira after he was dragged off by Takeru. Soon they encounter Tomoyuki, who is someone from Rin's past. But he just ignores him and tells him to shut up. Akira and Rin have a short conversation as they get back to the hotel and meet up with Motomi. There Keisuke sees Akira and is happy is okay. Rin comes with a bag full of solids and water and asks them if they want to do something fun. They all eat and chat on the roof of a building. At nighttime, Shiki appears and slays a group Line addicts. One person yells that he has appeared and Rin jumps at hearing his name. Akira runs after Rin but instead encounters Shiki in a nearby alley. They have a short fight, which Akira end sup on the ground. Shiki picks him up and pins him against the wall, asking if he really wants to die. He then starts choking him, but Akira fights back by folding up and kicking him away. Shiki is amused by this and tells him he'll play with him again soon. As he walks off, Akira is oddly energized by this and states "So that's... Shiki."

A man (in the shadows) murders everyone in a club, meanwhile Takeru drinks Line. Akira goes around the city searching for Keisuke, Rin is back at the hotel, and overhears a conversation between line users. Akira continues to search and discovers the bodies of the men in the club, to which he is sickened. While walking into an alleyway he is attacked and beaten by Takeru; Takeru licks Akira’s blood and begins to choke then slowly retreats. Rin and Motomi have a conversation about drugs/city/life. Takeru thinks about his sister and regrets leaving her, but dreams of winning Igra for his family. He is then discovered by Keisuke, who superpowered on line, crushes Takeru's skull. Keisuke then goes to meet Akira; whom he knocks out and then carries him off.

Keisuke shows Akira all the tags that he gotten, and stating his desire to see more emotions, particularly the “troubled, agonized, dying” face. They begin to fight, throughout the battle Akira tells Keisuke how he really felt all this time which angers Keisuke even more. Akira gets his weapon knocked out of his hands causing him to get cut and bleed. Some blood gets onto Keisuke’s face and mouth which causes him to suffocate. Akira get some black flashes of his past, and snaps back into reality. He finds out that Keisuke is still alive and brings him to a bed, Akira watches over Keisuke until sun rise where Rin finds them and takes off with their tags in order to fight Il re.

Rin prepares to fight Il re which turns out to be Shiki but gets defeated quickly, Akira comes to the rescue as the military begins to bomb the place. Shiki saves Arbitro and questions him about Akira. Rin and Akira takes shelter in a abandoned warehouse where they agree to meet Motomi at the church, Gunji and Kiriwar shows up. In order to escape, the two of them splits up, Gunji goes after Akira while Kiriwar goes after Rin. Akira gets beaten up badly and before he is killed, N comes to the rescue and carries him off to where Keisuke is. *Backflash* Akira meets Nano as a younger boy, in exchange for a promise to meet again, N gives him a knife *back to present* Akira wakes up and finds Keisuke unconscious. Emma and Gwen shows up as they are on a mission to bring Premier (Nano) back with them, Emma admits to framing Akira for the murder and got him stuck in Toshima. She shoots Gwen for getting in her way then before she shoots Nano, he uses his arm to pierce through her body. Shiki shows up while Akira gets Keisuke and prepares to escape.

Shiki fights Nicole Premier, and ends up drinking Nicole's blood, from which Line is made, which would normally drive people crazy or kill them. Shiki survives and goes looking for Akira. He finds Akira and Keisuke as they are fleeing to safety. When Shiki tries to force Akira to come with him, Keisuke tries to protect Akira, but is killed by Shiki.

After Keisuke's death, Nicole Premier appear, the fight between Shiki and Nicole Premier continued.