Sivakarthikeyan, Hansika Motwani
The movie begins with 5 Chennai-based IT employees Sandy (Sathish), Joe, Gokul, Vaishnavi aka Vaishu and Nikita meeting a siddhar at the Chandragiri forest, who has the power to grant wishes to those who request for them. Sandy, who is sceptical about the siddhar's powers, asks him for a copy of the Daily Thanthi newspaper dated on the day after Ayudha Puja (no newspapers are printed during Ayudha Puja). To his surprise, the siddhar materialises the requested copy. The gang then read the materialised newspaper and find out to their shock that the company which they work for (Satyam Computers) would close down the next day. When this does happen, they accept the credibility of the newspaper and decide to make money through it. While Nikita is perusing the paper, she sees an article where one Peter who stays in Royapuram wins a boxing tournament on 2 October and dedicates the prize money of ?2,00,00,000 to the 5 of them. The gang is astounded on reading this news and decide to find this Peter and sponsor him for the boxing tournament, with the hope of getting ?2,00,00,000. However, they soon find out that the cash prize for the winner of the tournament is only ?1,00,000 and that AirAsia is not interested to sponsor the tournament (As per the newspaper article, AirAsia sponsored the boxing tournament). Nevertheless, they are still hopeful, due to the newspaper article.
The gang successfully manage to track down Peter (Sivakarthikeyan), but immediately find out that he is no boxer and in fact knows nothing about the sport; he is just an ordinary youth who hates sports, cares little about life and spends his time drinking. However, he is in love with a young woman Yazhini (Hansika Motwani), who loves sports. He accepts their proposal in order to impress Yazhini, but refuses to start training until they fulfill his desires such as buying him a new motorbike and fridge (for exclusively storing alcohol), painting his house and helping him win Yazhini's heart, all of which they reluctantly (and successfully) do. Soon, Peter, with the gang's as well as Yazhini's support, starts training, but shows no interest, often going late to the gym in the mornings and then fooling around in the gym as well. Later, the gang find out that there is another boxer by the name of "Killer" Peter (Vamsi Krishna) who also resides in Royapuram like the Peter they are sponsoring, but is a champion boxer who has even killed some of his opponents in the ring. Thinking that they are sponsoring the wrong Peter, the gang approach "Killer" Peter and offer to sponsor him, but he refuses. They eventually decide (albeit reluctantly) to continue sponsoring the Peter they are currently sponsoring.
Soon the boxing championship starts and Peter somehow manages to win all the preliminary matches by fluke, by using a technique wherein he uses his nimble and agile body to escape being hit by his stronger and more experienced opponents, eventually causing them to inadvertently get disqualified or knocked out. The media give a name for his technique: "Maan Karate" (after a dialogue spoken by Dhamu in the film Gemini, which means "running for life"). Peter soon becomes known as "Maan Karate" Peter (to distinguish from "Killer" Peter) and becomes an Internet sensation overnight, winning a lot of fans. However, he bars Yazhini from seeing his matches, thinking that he would be exposed as a phony if she were to see his matches. Later, the prize money is raised from ?1,00,000 to ?2,00,00,000 and AirAsia joins in as the main sponsor of the tournament, which excites the gang, who now feel that their dreams will come true with "Maan Karate" Peter after all.
Eventually, Peter enters the final of the tournament, where he is to face "Killer" Peter. "Maan Karate" Peter becomes upset on entering the final and starts fearing for his life, feeling that due to his lack of boxing skill, he is actually going to be killed by "Killer" Peter, a much more experienced, skilled and powerful opponent than him, during the final. He tries to back off from fighting in the final by trying to injure his hand (which is unsuccessful) and also trying to tell Yazhini the truth that he is not a boxer (but backs off at the last minute after Yazhini expresses her confidence in him). In a last-ditch attempt, he meets "Killer" Peter at his house and tries to convince him to "throw" the match so that he could win and make Yazhini happy, but is brutally beaten up and humiliated by him in response. Determined to avenge being insulted, "Maan Karate" Peter gains confidence and starts training hard for the first time ever, with the main goal of knocking out "Killer" Peter in the ring. He also ensures that Yazhini sees the final. Meanwhile, unknown to him, the IT gang who is sponsoring him have switched sides and have decided to support "Killer" Peter after being offered ?75,00,000 by "Killer" Peter's father-in-law (who is impressed as to how the IT gang had successfully predicted the outcome of the boxing tournament so far), feeling that it is better to trust a professional boxer like "Killer" Peter than a simpleton like "Maan Karate" Peter. Only Nikita is against betraying "Maan Karate" Peter, but she too reluctantly accepts the decision of the rest of the gang.
On the night of 2 October, the final begins. "Killer" Peter immediately gains the upper hand, pummelling "Maan Karate" Peter with heavy blows, severely weakening him. However, he is not daunted and continues to put up a brave fight, but is soon on the verge of being knocked out. Nikita is distraught on seeing "Maan Karate" Peter being assaulted so badly and reveals the truth to Yazhini that "Maan Karate" Peter is no boxer and had actually entered the finals by fluke. Yazhini immediately tries to call off the match, with the assurance that she is not mad at "Maan Karate" Peter and that their relationship will continue irrespective of the lie, but he refuses to listen to her. Once again remembering how he had been insulted by "Killer" Peter, he soon manages to fight back, eventually knocking him out, causing a major upset. "Maan Karate" Peter wins the boxing tournament and dedicates the prize money of ?2,00,00,000 to the astounded IT gang, who were walking out of the stadium after seeing "Killer" Peter lose, but they deny the offer. He also conveys his love for a sobbing Yazhini, who is relieved that he has survived.
The movie ends with a display of a portion of the newspaper the siddhar had materialised torn by Nikita and left at the Chandragiri forest several months ago. The portion shows a photo of "Maan Karate" Peter lifting the boxing tournament trophy.