At the Kanyakumari beach, Geetha (Shriya Saran) looks at a lonely lying personal diary where she enjoys a poem written in it. She admires the poem by relying on the same page. While she and her friend admire the beauty of the sunrise, she accidentally loses one of her anklets (it falls in the sea). She sees a person jumping in after it, and she perceives him to have died in the waters. The incident haunts her in her dream again and again, and she feels very guilty for it. Back to the present in Chennai, Geetha eventually meets a rich, handsome boy Arjun (Sameer Dattani), in her college, who impresses her to win her love. He proposes to her and threatens her to love him or else he would die by jumping from the college rooftop. Already feeling guilty for being the cause of a person's death, not willing to let it happen again, Geetha accepts his love and screams "I love you" in front of the entire college to Arjun, which was witnessed by Kutty (Dhanush).

Kutty proposes his love for Geetha in front of Arjun, which shocks Geetha and annoys Arjun. Geetha turns down his request again and again and reminds him of her relationship with Arjun. However, Kutty instead tells her that it is not an issue to him and tells her to continue loving Arjun and he would never stop loving her. Arjun is irritated by Kutty's acting. He fights with him in order to bully him into stopping but instead was challenged by Kutty that if Arjun is confident in his love, no one would separate Geetha from him. Arjun finds no option but to accept in order to prove his confidence in his love (else accept that his love is weak). Kutty pulls all kind of stunts to impress Geetha (including winning a rigged race in order to protect Geetha's chastity from Arjun) but fails to make her accept his love.

Meanwhile, Arjun introduces Geetha to his father (Radha Ravi) expecting him to approve and bless their marriage, but his father, seeing to further his political ambitions, engages a minister's daughter (who is shown to be a spoilt girl of questionable character) for Arjun. So Arjun escapes with Geetha, who is helped by Kutty. Kutty, Arjun, Geetha are chased by Arjun's father's men but are unable to catch them. Meanwhile, old wounds renew between Kutty and Arjun. After an intense (kung-fu) fight with the henchmen (where Arjun runs and Kutty fights), Arjun leaves Geetha with Kutty without saying anything to either of them. Kutty takes care of Geetha, which touches her. She soon realizes the love he has for her and regrets not having met him before her commitment to Arjun. She tries telling the same to him, but Kutty, thinking that Geetha is scolding him, closes his ears and does not hear what she actually said to him (he does that a couple of times in the movie).

Arjun arrives at the scene with his father in tow, now all happy for their marriage. Geetha leaves with Arjun to marry him. On the wedding day of Arjun and Geetha, Kutty wanders here and there to look after wedding-related works. His friends understand his internal pain and slap him, begging him to cry at least now. While Geetha is on her way to the ceremony, Kutty stops her and openly expresses his pain of his love and how he is going to miss her and asks if his love did touch her at least once, without knowing that his love touched her already. He then laughs and passes it off as a prank. Geetha stares speechless with helplessness. Kutty's kid friends present Geetha with a gift from Kutty. The gift turns out to be Geetha's lost anklet and the poem page where she wrote a reply while she was in Kanyakumari. Kutty was the person who jumped into the sea to take her anklet and was assumed dead by Geetha. Geetha finally realizes her love for Kutty, rejects her marriage with Arjun, and goes to Kutty and accepts his love finally by hugging him.