Akku is about the story of a man named Siva, who is an IT professional that instantly falls in love with a positive and upbeat girl named Bhanu. Her brother is a terrorist who plans on bombing the city of Chennai. One day, Siva and Bhanu decide to elope, but unfortunately, Bhanu's older brother finds out and holds them both captive. Her brother decides to bomb the city as a way of showing his revenge on Siva. He uses Siva as a suicide bomber by planting a bomb on his shoe and sends him running into the city. If he slows down, the bomb will automatically explode, killing millions of people around him. Once the city bomb squad learns about this and tries to defuse the bomb and save Sinu. However, after they disable the bomb, many strange twists begin to happen.