Shankar is a graduate of BSC nautical science waiting for a job in the shipping industry. He is a tenant in the house of Bhanu, a medical student who is also his good friend and confidante. They spend almost all their time together, and she seeks him out as a refuge due to her stepbrother Panneerselvam, whom she dislikes but is forced to live with. One day, while dropping off Bhanu at a bus stop, Shankar spots a pretty girl named Sarika and is drawn to her. They soon discover that she is interested in him as well, and they fall in love during their daily bus rides. Meanwhile, Shankar’s rude and abusive father Chidhambaram arrives in Chennai for his wife's heart surgery and tells Shankar that his marriage with a girl is being arranged swiftly, and the same pressure falls on Sarika’s family as well. The two are unaware that they have been chosen for each other by their parents, leading them to avoid the formal meeting ceremony. Chidhambaram’s temper triggers a confrontation at Sarika’s house, and after a heated dispute, both sets of parents cancel the marriage plans.
Panneer misreads Bhanu and Shankar’s closeness as love, and he tells Shankar’s parents, demanding their consent for marriage. To pacify his ailing mother until her surgery, Shankar and Bhanu momentarily go along with the idea, but the arrangement quickly entangles more trouble. Misunderstandings mount when Panneer catches Bhanu and Shankar together again and reveals the supposed engagement to Sarika, who then ends things with Shankar.
To clear the air, Shankar asks Bhanu to explain the truth to Panneer, but Bhanu reveals she has loved Shankar for years and had used the arranged marriages to influence outcomes. She explains she sacrificed her own feelings when she believed Shankar loved Sarika. Yet after a sequence of misjudgments—including the failed match with Sarika—Bhanu believes she belongs with Shankar.
Shankar insists he does not share Bhanu’s feelings, but Bhanu refuses to listen. In a turn of events, Sarika learns from bus driver Vellaisamy about Bhanu’s role in the confusion, realizes Shankar is innocent, and reconciles with him. Bhanu’s anger flares; to keep Sarika away from Shankar, she allies with Doss, Sarika’s stalker who has previously been refused by her. Together with Doss and his friends, Bhanu watches as Sarika’s new saree is teased and yanked off in public.
Bhanu, witnessing this, brings Sarika home under the guise of offering comfort and new clothes, but to Sarika’s horror, she reveals her true identity and uses blackmail to push her away. Sarika, devastated and humiliated, attempts suicide by poison. Panneer overhears the conversation, realizes his mistake, and condemns Bhanu for her selfish actions. Sarika is rushed to the same hospital where Bhanu studies, but a doctors’ strike leaves her without treatment. Bhanu’s friends push to help save Sarika, and Shankar learns the truth and confronts Doss.
Shankar arrives at the hospital after Doss reveals Bhanu’s role, only to find Sarika being treated by Bhanu herself. He begs Bhanu to save her in exchange for a future marriage. The operation is a success, and as they walk out of the room, Bhanu tells Shankar that her love for him has faded after seeing how far Sarika would go for him, making it impossible for Bhanu to find a place in his heart. She apologizes, and Shankar forgives her, choosing to be with Sarika. Bhanu also finds peace with her brother Panneer and accepts his affection for her.
