Unnodu Ka opens with a clash between two families in Sivaganga. Jayavel (Prabhu) and Keerthy Vasan (Thennavan), the heirs of these families, are expected to take on each other, and thereby safeguard the village's 'tradition'. However, they are actually thick friends, and have no clue about the feud, which has been prevailing for five generations. They leave to Chennai with their respective families in search of a peaceful life, and settle there as neighbours. Jayavel's son Siva (Aari) and Keerthy Vasan's daughter Abhirami (Maya) are brought up together. Interestingly, the two were born on the same day, though Abhi was born just a second before Siva — one of the reasons for her overbearing attitude towards him. Their parents hope they get married to each other, but the two are often found quarrelling. However, they realise their true feelings for each other when they try to help out their friends, Bhagat Singh (Bala Saravanan) and Sundarambal aka Su (Misha Ghoshal).
Meanwhile, a few disappointed villagers who have been 'missing the action' for a while, come to the city to know the 'status' of rivalry between Jayavel and Keerthy Vasan, and take them back to Sivaganga to settle the issue once for all. So, what happens to Bhagat Singh and Sundarambal's romance, which her father (Mansoor Ali Khan) doesn't accept? Do Siva and Abhi marry and make their parents' dream come true? Will Jayavel and Keerthy be able to save the village from further damage?
The story by Abirami Ramanathan has scope for a better entertainer, but the flow of sequences is sluggish for most parts of the first half. The cinematography by Naga Saravanan deserves appreciation, especially in the scenes shot in the village. The village portions in the film are a relief and elevate the drama in the story compared to the other portions, which are a bit loud. The scenes involving Prabhu and Urvashi (who plays his wife) needed to be livelier and engaging.
As for the actors, Aari and Maya put up not-so-bad performances. Bala Saravanan fits the bill, and manages to entertain in the scenes in which he appears, while Misha, as his lady love, is OK. Mansoor Ali Khan does what is expected of him, and MS Bhaskar is apt in the brief role of a kidnapper.