The film begins with Kanyakumari (Sneha) and her son Shakthi being ambushed by some foreigners. When one of the foreigners beats her son, Kanya gets enraged and plucks out the foreigner's larynx, which is noticed by the police nearby. Kanya is arrested and sent to jail for 16 years.

We are taken to the present, where Shakthi (Dhanush) and Puncture (KPY Sathish) are robbing an MMA academy. The owner of the academy, Nilan (Naveen Chandra), gets upset when he finds out that his trophy is missing and calls the police in to investigate. The police, in turn, call Shakthi and Puncture, only for the two to become informers for the police and find out the robbers who robbed Nilan's trophy (the police officers do not know that it was Shakthi and Puncture who robbed the trophy). They are forced to work with Sadhana Sha (Mehreen Pirzada), the owner of their opposite house and with whom they have an enmity. Later in the film, it is revealed that Shakthi and Puncture robbed the academy, knowing the fact that Sadhana was kept in charge of it, hence humiliating her. Meanwhile, Kanya is released from jail and follows Nilan, planning to kill him. She follows him until his gym, where she sees Shakthi, who she thought, got killed when the foreigner hit him. Nilan finds out that she is attempting to kill him and tries to capture her but in vain. When Kanya comes to Shakthi's house in searching for him, Sadhana, unbeknownst to her, sets up Kanya and leaves her to get attacked because Nilan, her boss, instructed her to do so. When thugs arrive at Kanya's location to kill her, Shakthi comes to her rescue and, in the process, finds out that she is his mother. He then finds out his past.

Dhiraviyaperumal (Dhanush) is a skilled Adimurai warrior and Shakthi's father, who is taught the art by his master Muthaiah Asaan (Nassar), who is also Nilan's (actual name Nilapparai) father. Nilan's father, who himself is a skilled Adimurai warrior, keeps degrading him because Nilan is not able to learn Adimurai, which leaves Nilan frustrated. Even though Dhiraviyaperumal and Nilan are friends, on hearing his father continuously compares Dhiraviyaperumal's feats with his own, Nilan gets agitated. When Nilan is forced to fight Kanya, who also stays in the village, and she defeats him, he is very humiliated, and he leaves the village.

Dhiraviyaperumal soon realizes that Adimurai is only known to their village and is not known to Tamil Nadu when his disciple commits suicide when he is refused the job of a police officer. He decides to open a school that teaches Adimurai and gets the minister to agree. Meanwhile, Nilan comes back from abroad as a kickboxing champion and plans to recruit people to learn kickboxing. On confronting the villagers, he beats a boy, which leads to a fight between Nilan and Dhiraviyaperumal; if Nilan wins, he can teach kickboxing, and if Dhiraviyaperumal wins, Nilan has to fall at the feet of the boy he hit and ask for forgiveness. Dhiraviyaperumal defeats Nilan, and in retaliation, Nilan kills Muthaiah Asaan and poisons the food of the village. He then burns down the village and Dhiraviyaperumal to death. Kanya escapes with her son Shakthi, leading to the events in the beginning.

Shakthi swears revenge and enrolls in the MMA event organized by Nilan. He is trained by his mother, Kanya, in the art of Adimurai. On the day of the event, Nilan uses a convict from Thailand who has killed four people in the ring to fight with Shakthi. Shakthi defeats him, but the convict stabs Shakthi in the right shoulder. He still fights the next opponent and emerges victorious as he is ambidextrous. Nilan asks his son Richard to use unethical methods, to kill Shakthi, but Richard refuses and forfeits the match. Sadhana eavesdrops on Nilan and tells Shakthi, but ends up getting smashed into a glass table. Due to this, she is rushed to the hospital. Nilan then challenges Shakthi, and while Nilan has the upper hand initially, Shakthi defeats Nilan and lets Nilan go, like his father. The film ends with Shakthi winning the championship and giving a speech on Adimurai and its importance, followed by the acceptance of Adimurai as a sport by the Tamil Nadu Sports ministry, thus achieving Dhiraviyaperumal's dream of spreading Adimurai throughout Tamil Nadu.