Rajesh Shivakumar and Sam are students at an engineering college in Ooty. Sam is a top-performing student who is popular with the students and faculty, while Rajesh, an underperforming student, is notorious for his rebellious, violent and misogynistic attitude. This contrast in personalities puts the two students at loggerheads throughout their college days, with both of them engaging in constant fights and pranks with each other. Upon graduating, Sam and Rajesh decide to never see each other ever again. Sam goes to the United States as he has secured a job while Rajesh decides to stay in India.
Two years later, Rajesh is a software engineering instructor in Chennai and roams around in his free time with his close friend Chockalingam "Chokku". He stays with his grandfather Subbuni, a librarian from the Aminjikarai neighbourhood of Chennai. Rajesh's affection for his grandfather is such that he even refuses to accept an on-site opportunity in Singapore so that he can be with him. While on a trip to Bangalore, he comes across a young woman dancing with children in the rain and gets immediately smitten by her when he sees her face lit by the flash of a lightning bolt. He comes across this woman again during a friend's wedding and soon learns that the woman's name is Reena Joseph and she works as a chartered accountant at Ford, Bangalore. Some days later, Rajesh, who is back in Chennai, notices Reena again, this time exiting a Ford office cab. He and Chokku pursue Reena, but lose track of her in a mall.