Plot

A young man Ajay (cancer victim) meets two lovely women Renu (wife) and Vidya (journalist) in his life.

An inquisitive girl, Vidya falls in love with Mano's impulsive "do it now or hold it forever" philosophy, without knowing anything about him or where he came from. When she proposes to him, he instinctively decides to flee the city. But destiny stops him. As Vidya travels with him to America, we discover his story, his love, his plight, and his need to live a life of anonymity.—Aarthi Sriram

Dr Ajay "AJ" Kumar comes to Hyderabad (Chennai in the Tamil version) and introduces himself as Mano. He rents a house owned by elderly couple S. V. S. Murthy and Jayam. A do-gooder, Ajay lives life with a purpose. He gets along with everyone and wins the hearts of those whom he is close with. D. "Vidya" Vidyalakshmi, a newspaper photojournalist, gets acquainted with him. Ajay is the sort of person who finds satisfaction in helping others. He sponsors the education of street children with the help of Vidya, who is attracted by his good nature. Things take a turn when she tells him about her feelings. Ajay, without informing her, decides to leave the city.

Meanwhile, a flashback reveals that Ajay was a doctor in San Francisco, where he meets Renuka "Renu" Narayanan, an interior designer. They get married only to be told months later that Ajay has pancreatic cancer and has about six months left - hence the title 180 (180 days). As Ajay is about to leave Chennai, Vidya meets with an accident and has to be operated upon. Ajay takes Vidya to San Francisco for treatment. While in San Francisco, he meets his friend RJ "Sam" Sambasivam who asks him to meet Renu, but Ajay leaves as he sees her life happier without him. It is revealed that Ajay had faked his death to make Renu believe that he had died so that she would not suffer thinking about him every day. Now seeing her contentment, he decides not to meet Renu. He misses his flight to India and goes to Brazil instead. Now in Rio de Janeiro, he goes by the name Jose. He is seen playing football, waiting for his death.