Saraswathi "Yamuna" (Suvalakshmi), one of two daughters of an Orthodox father (Poornam Vishwanathan), comes to Madras for finishing her studies. Major Madhavan (Prakash Raj) is the husband of Yamuna's elder sister Ganga (Rohini (actress)), who infatuates about Yamuna after seeing a photo in a letter sent by her. Meanwhile, Yamuna meets Jeevanantham (Ajith Kumar) in a bus, who gives his ticket to her as she had not taken her own. Later one day, Jeeva decides to express his love to Yamuna by writing "1 4 3" (the number of letters in "I love you") in a letter and giving it to her, but he witnesses a group beating a boy who did the same thing, so he crumples the letter, and it is found by Yamuna, who realizes his love. One day when they were walking together, Jeeva tries to remove the dirt from Yamuna's eyes, and he kisses her. Yamuna is angry with him. Jeeva senses it and gets wet in the rain and gets a cold. Hearing this, Yamuna meets him. Jeeva expresses that she is the only medicine to him, and he needs her. Yamuna promises she will marry him. On Yamuna's birthday, Jeeva jumps into her house and presents her a puppy. One day, fearing that Yamuna's father might not marry him to Yamuna, he decides to marry her in a register office, but Yamuna refuses and Jeeva leaves.