Billu is the son of Chidambaram, a figure deeply loved and respected in Royapuram, where the community treats him almost like a guardian. [Billu] forms an instant connection with Susi when they cross paths at the railway station, and [Susi], who has just arrived from Bangalore to Chennai, is set to stay at Settu's place. [Settu] has long worked for Susi's father, [Chidambaram], a feared criminal, though he has since changed his ways and still carries the old respect for him.
[Susi] longs for love and care, and is touched by the close-knit bond among the Royapuram residents. A godman prophesies that Susi is the one for Billu, a prediction that startles her and stirs fear about how her father might react. Yet she cannot completely hide her feelings and relishes Billu’s company and that of his friends, until the unexpected turns begin to unfold.
[Susi] acts peculiar when a long-lost friend meets her at a restaurant. She denies knowing her, despite Revathy's attempts to talk to her. [Revathy]'s efforts are met with confusion, and she walks away, leaving Billu and his friends puzzled. Susi then reveals the truth: she is dealing with PTSD after an accident and has memory gaps spanning three years. Billu accompanies her to a physician, Dr. Devasaghayam, who explains that the condition is treatable, but if she is cured, she may not remember what happened or who she met in Chennai, including Billu.
This possibility weighs heavily on Susi, who pleads with Billu to promise that he will never leave her, even if her memory fails. Billu makes that vow. His conversation with Chidambaram is met with anger from the father, and he travels to Chennai with his goons. The locals rally to defend Billu’s cause and resist the family’s plans. In a strategic move, Chidambaram agrees to the engagement between Billu and Susi, then ambushes Billu and moves toward Bangalore with Susi, leaving the Royapuram community stunned.
When Billu finally confronts Susi at her new residence, he is shocked to learn that she has recovered but does not recognize him. He clings to his promise and brings her back to Royapuram, hoping memories will return. Chidambaram arrives with his men, prompting a tense clash. Billu is disheartened as Chidambaram more or less drags Susi away, while she begins to see the supportive faces of the Royapuram residents and the life she might reclaim. She unexpectedly departs from her father, running toward Billu with a new spark of recognition. Although she claims she cannot recall their shared past in detail, she trusts what Billu has told her about life in Chennai, and in the end, the couple reunites to face whatever comes next, together.
