Kaakki Sattai has Murali (Kamal Haasan), a young man who trains very hard to become a police officer. Uma (Ambika) is his neighbour and they fall in love with each other while Uma supports Murali to achieve his goal but he is rejected after the physical test due to not having influence or money.
Angered by the rejection, Murali turns into a local rowdy. He causes trouble in his district and comes to the attention of a notorious smuggler and murderer, Vicky (Sathyaraj) and his partner Anand (Rajeev). After initial conflict between the two, Vicky recruits rowdy Murali into his gang. Murali becomes his most trusted member. He grows intimate with a girl, Anita (Madhavi), who is looking for personal revenge against Anand.