The story starts two years after the end of high school iron fist legend, the main protagonist Kiichi Miyazawa “Kiibo”, became the heir of his family’s martial art Nadashinkage-ryu after the previous one his father Seiko Miyazawa suffered a crushing defeat at the hands of his evil twin brother and Kiichi’s uncle Kiryu. In order to pay for hospital bills Kiichi has turned to fighting in illegal underground matches called dark fights in which almost anything is allowed. Kiichi has become a mainstay in these fights, not only because of his outstanding victories but that he refuses to seriously injure any of his opponents, upholding his father’s teachings of never kill anyone.
During one particular match in which Kiichi was on the verge of losing, his uncle appeared only to see the progress of his nephew’s training and to tempt him into using a killing technique on his adversary. Refusing to give into such treachery Kiichi manages to score a win, it was during this fight that we are revealed that Kiichi mistakenly killed an opponent during an MMA (Mixed Martial Art) tournament using a technique that Kiryu taught him. That and the fact that he crippled his father are the main reasons that Kiichi must defeat his uncle.
At the end of Kiichi’s last match a secret sect of monks called the Hagyu have sent one of their own students to end the Nadashinkage style and its current practitioners, Suzuki “The Wind” Minoru is the one chosen to defeat Kiichi. Elsewhere several benefactors have formed into starting another MMA tournament called the Hyper Battle, which is held once a year in order to find the world’s strongest fighter, a title which is held by one called the Battle King. Kiichi at first seems uninterested but later relents and starts training in order to participate, after challenging students at a karate dojo he comes face to face with the one sent to eliminate him “The Wind” Minoru. After testing their abilities Minoru starts to respect him and asks Kiichi to take him to meet his father. It is here that we are shown the consequences of losing to Kiryu. Seiko Miyazawa “The Quiet Tiger” is shown in a childlike state, barely able to feed himself and at times necessitating the use of a wheelchair, he is suffering from a condition called Apraxia.
Wanting to help the man who once defeated the Hagyu, the wind starts treating him himself with knowledge of acupuncture and pressure point massage, in the past Seiko was challenged by the Hagyu school but made the fight look like it ended in a draw in order to make the school not look bad, Minoru was one of the few to take notice. After much treatment at Minoru’s hands Seiko starts to recover from all his conditions baffling all the doctors at his miraculous results. Seiko gives a heartwarming thanks to his son Kiichi for taking care of him these past two years, Kiichi tells his father that the one who cured him has already left, Minoru is seen walking away with an invitation to the Hyper Battle. Later that night Kiichi bids his father a farewell as he goes to participate at the Japanese preliminaries for the Hyper Battle.
Meanwhile at the sacred Shikabane (corpse) mountain many fighters gather at the preliminaries for the Hyper Battle, among them are many fighters of high renown to the lesser known are fighting for a chance to compete. Kiichi during the extent of 24 hours battles many opponents in order to guarantee a spot in the Hyper Battle, becoming a finalist. Meanwhile, Seiko is shown training once again but he seems to be wracked with feelings of revenge and anger towards Kiryu for what he did to him, and vows to get even with him. After being discharged from the hospital he goes to the apparent resting place of his oldest brother Son-O Miyazawa, who was thought to have been killed by Kiryu many years before and ends up being abducted by a mysterious group of individuals.
Afterwards Kiichi travels to New York City where the Hyper Battle will be held. After meeting up with an old friend he goes to Madison Square Garden where the competition will take place, he encounters many fighters among them Minoru, Kiryu who will do an exhibition fight, his father Seiko who was training with a group called “Team D” and the Japanese Brazilian fighter Mauricio “Jet” Naito who is also a deaf mute. It is at this tournament Kiichi will ultimately have to push the limits of his strength and skill in order to better himself as a fighter and martial artist in that he will end up fighting either Mauricio or his own father “The Quiet Tiger”