Niranjana is the daughter of Samuthiram, Tiruchirapalli's most feared rowdy who works as the minister's manny. When the minister calls Samuthiram to come to one of his factories alone to deal with a personal matter, Samuthiram arrives and grows suspicious that no one is there. He phones his second-in-command Ravi to send someone to check on him. Meanwhile, the minister's goon Shankar and his gang arrive and kill Samuthiram for meeting with the opposing minister. Guna, sent by Ravi, reaches the scene and finds Samuthiram dead. The gang holds a funeral with Samuthiram's family, and Ravi swears loyalty to them. Guna kills Vetri, a goon from Shankar's gang, for becoming an approver.
Meanwhile, Niranjana endures harassment at her college bus stop for weeks. Her mother asks Ravi to send someone to take care of it, and Ravi assigns Guna to guard her until she finishes college. Guna slashes the guy's arm, but the attackers threaten to throw acid on Niranjana if he does not recover. Guna is tasked with following and keeping Niranjana safe until graduation. She slowly falls in love with him and proposes to him, but he refuses, saying that love will not work for him and that the town’s people fear and respect him for his weapons. She dares him to spend a day without any weapons. He tries, but learns that Shankar's men are following him on that very day.
The next day, Niranjana asks Guna if he was scared even for a minute because he had no weapons. She tells him that he was not fearing the enemy but their weapons, in the same way the town's people are afraid of his weapons and not him. She tells him to come out of this delusion and seriously consider starting a life and family for himself. She also says she will wait for him until then. Guna then begins to reciprocate her feelings. He tells Ravi about his love for Niranjana, but Ravi tells him to forget her as it is not appropriate.
Meanwhile, Shankar's gang follows Guna to kill him, and he gets stabbed but survives with the help of Dr. Chandran. Niranjana's family learns about Guna's relationship with her and refuses to accept it. Guna gets into a scuffle with Niranjana's brother. Shankar's gang tries to kill Guna again, and Guna ends up killing Shankar and eloping with Niranjana to Thondi while Ravi and the police continue to search for him. Guna asks Chandran to fetch ₹7 lakhs, his passport, and his mother's wedding chain from his home, and Chandran goes to Guna's house. One of Ravi's men informs Ravi about someone's presence in the house. Ravi and three of his men wait outside to stab the man as they think it is Guna. They stab the man, who turns out to be Chandran. Ravi asks where Guna is, but Chandran refuses to tell, and Ravi tells him to tell Guna that he will find them and bring Niranjana home by killing Guna even if it takes 10 years and lets Chandran go.
Guna is furious that Ravi, whom he thought of as his own brother, tried to kill him. He goes to Trichy, where a chase and fight ensue between Guna, Ravi, and his gang, with Guna gaining the upper hand and slashing Ravi multiple times. Ravi asks Guna to kill him, but Guna cannot bring himself to do so. He takes him to the hospital. Guna also convinces his friend from Shankar's gang to leave the violent life behind and join him. The film ends with Guna, Niranjana, Chandran, and his girlfriend, having married and Ravi with his wife and children coming to Niranjana's home and her mother taking an aarti to everyone.
