Arivu (Sivakarthikeyan) hails from Kolaikkara Kuppam aka Cooliekkara Kuppam a slum area in Chennai. He is one such responsible youth, who wants to focus on the upliftment of his fellow beings and he works hard for the same. Arivu starts Kuppam FM 90.8, a local radio channel with the help of the area gangster Kasi (Prakash Raj). In reality, Arivu tries to free the people of the area from the atrocities of Kasi, who is deliberately preventing them from becoming independent, so that he may continue to dominate the area. Arivu succeeds in turning the people of the area against Kasi, thus destroying his support.
Later, Arivu joins a leading FMCG company, Saffron and joins its sales department under Stella Bruce (Thambi Ramaiah). He also manages to bring his friend Bhagya (Vijay Vasanth) out of Kasi's gang and gets him a job in Saffron. He meets Aadhi (Fahadh Faasil), the Brand Manager of Saffron, who teaches him how to progress by doing smart work and Arivu considers him as his inspiration. On the night of April 1, Kasi and his gang attack Bhagya and brutally stab him in Saffron's godown (warehouse), whereupon he dies in the hands of Arivu. Arivu filled with rage, tries to attack Kasi. But, Kasi's rival Doss (Sharath Lohitashwa) attacks and brutally stabs him in retaliation for their previous encounter and Arivu admonishes Kasi for being such a paid henchman. Kasi reveals to Arivu that he killed Bhagya on a contract given by Jayaram (Anish Kuruvilla) the President of Saffron company, due to the fact that Bhagya tries to help Kasthuri (Sneha), who files a case claiming Saffron's products to be adulterated, due to which she had lost her son. Arivu is addressed by Kasi as being a worse hitman than he himself is. Arivu then saves Kasi. Arivu is also told by Kasi that all the products manufactured by his company are adulterated. He takes up a mission to fight such malpractices not only in Saffron, but also in all the other five major food companies, including the company owned by Madhav Kurup (Mahesh Manjrekar). Arivu shares all of his plans with Aadhi. Meanwhile, it is revealed that Aadhi is actually Adhiban Madhav and he is the son of Madhav Kurup. He joined Saffron to know their trade secrets and merge the company with his father's company.
Arivu manages to convince the staff of his company to manufacture products as per Government regulations for two days, while he convinces the staff of the other companies to wear a kerchief on their dresses for the next two days, thus tricking the owners into believing that their workers have turned against them. But, Aadhi manages to foil this plan of Arivu and coerces the other owners to write over the major shares of their company to Madhav Kurup, thus making him the deciding authority of all their companies. Aadhi then manages to turn all the employees against Arivu by tricking them into believing that Arivu worked as a spy for Madhav Kurup. Stella Bruce then slaps Arivu and humiliates him, while Aadhi pretends to defend Arivu claiming that he is innocent and it is the new president who conspired all these. After this, Arivu reveals to Aadhi that Stella Bruce was his ally and he now knows that Aadhi is the true traitor. Aadhi then burns down the go down containing the unadulterated products and reveals to Arivu that he is the son of Madhav Kurup, and that he will be the next CEO of the company. He also convinces the staff through his clever tactics and makes them propose his name as the new CEO, also revealing to Arivu that he will make them manufacture adulterated products without their knowledge, now that he command their loyalty, support and trust.
Arivu goes to the Radio Mirchi radio station on the same day, which a night before May 1 and reveals that after the fire accident, one of the injured department heads of Saffron Karpaga Vinayagam (Ramdoss) called him into the ambulance and told him that he followed the regulations on the third day too. Arivu also got to know from the other team workers of Saffron Kennedy (Mansoor Ali Khan), Vinoth (Kaali Venkat), Ansari (Aruldoss) and Sivaranjani (Vinodhini Vaidyanathan) that after manufacturing quality products for two days, they could not bring themselves to manufacture adulterated products on the next day, and they all followed Government regulations, thus manufacturing quality products on the next day too. Aadhi now the CEO, hears the workers say that they will rebel against him and depose him if tries to revert to manufacturing adulterated products. Arivu further adds that the loyalty of all the employees in each and every field shouldn't be wasted by showing it towards unethical employers. Aadhi vents out his frustration on the permanent failure of his plan.
All the people in the city shows their support to Arivu. Arivu celebrates his success along with Mrinalini (Nayanthara) his love interest, his friends, his family, the people of his slum and the people of the city as the movie ends.