After a villager unwittingly prevents a number of terrorist attacks in Chennai, a young journalist identifies and persuades him to take on the disguise of a superhero to fight terrorism and corruption.

Siva (Dhanush) is asked to help a friend in a love marriage. Siva kidnaps Pooja (Genelia D’Souza) on a mistaken identity from the marriage hall. When Pooja is kidnapped, her uncles (both are from the Gounder community) and their henchmen follow them.

Sameer Behl (Shahid Kapoor) comes to Mumbai with Bollywood dreams, struggles through the day as a courier boy, and keeps failing in auditions for advertisements. More stereotypes are stuffed in as he refuses to take help from his dad in Delhi, is thrown out from his rented flat by the landlord, and comes away with his calculative companion. One day, a movie director named Rajeev Sharma (Mohnish Behl) sees Sameer dancing and calls him to his office. Soon, Sameer is signed as the male lead in his film, and his friend Tina (Genelia D’Souza) is selected as the choreographer on the same project. Homeless, Sameer sleeps in his car and works as a dance teacher in a school. Subsequently, Sameer loses his film and is disillusioned. Tina finds this out and asks him how he can spend his life like this. After some time, Tina tells him that she also quit the film and did not want to be the choreographer for that film because she saw him upset. Sameer realises the love Tina had for him. Tina encourages him to participate in a television talent-hunt show, the winner of which will win the same role that Sameer was to play. After some time, he agrees to participate in it. After filling up the contest form, he also says “I love you” to Tina. In his screen-test, Sameer dedicates his monologue to his mother. After his monologue, during the interview, he comes to know that his father’s shop in Delhi has been demolished. He promises Tina that he will come back for her and leaves to meet his father, heart-broken about the whole thing. After watching Sameer’s performance on TV, his father convinces him to go back to Mumbai and participate in the show.

Chirakkal Kelu Nayanar, a warrior in 16th century Kerala wants to avenge his father killed in a confrontation with Vasco da Gama and his troops and is assisted by his best friend Vavvali and warrior princess Ayesha.

Sachein (Vijay), a carefree and happy going guy joins a college in Ooty and falls for Shalini (Genelia) immediately on seeing her in first sight. Shalini studies in the same college as Sachein and is considered a popular and beautiful student, while also being a short tempered and arrogant girl with an upper-middle class status. Sachein comes to know all of this information about her from Arnold aka Ayyasamy (Vadivelu), who is a guy that studies in the college for about nine years and keeps studying there because he thinks that students should give their respect to their college professors, while also informing Sachein, that there are so many boys trying to impress her. This makes Sachein take a different route and he starts mocking Shalini in front of her, which irritates her. Slowly, they both become good friends, after Sachein saved her father in a bike accident. Santhanam (N. Santhanam), who is another student in the college also loves Shalini. But, he feels jealous seeing her and Sachein being good friends and decides to separate them. Santhanam writes in one of the walls of the college, that Sachein loves Shalini and this angers Shalini, as she misunderstands that only Sachein has done it. Shalini shouts at Sachein, but Sachein informs Shalini, that he is so outspoken and does not want to write in the college wall to convey his love, which makes Shalini realize her mistake.
But to her surprise, Sachein informs that, although he has not written it, but the content present on the wall is true which means that he is in love with Shalini. This again angers Shalini and she shouts at him that she considered him only as a good friend and that she wasn’t in love with him. Later, Shalini overhears Sachein challenging Santhanam that Shalini will convey her love within the next thirty days, as their college years will be completed by then. Shalini challenges Sachein that she will never fall in love with him.
Manju (Bipasha Basu) is also from the same college and she likes Sachein. Shalini gets jealous when she spots Sachein and Manju together often. But Manju informs Shalini that Sachein loves Shalini so much and asks her not to hide her feelings, as it is very evident that Shalini too likes Sachein. This makes Shalini realize her love towards Sachein. Sachein comes to know that Shalini’s parents have arranged a wedding for her and he meets Shalini on the last day of their college and says that he has lost the challenge and he will be leaving Ooty tomorrow. But Shalini hides her feelings towards Sachein and she plans to propose her love the next day as she wants to win the challenge by not conveying her love within the 30 days.
On the 31st day, Shalini is excited and goes to propose Sachein. But suddenly, she meets Gowtham (Raghuvaran) on the way, who is Sachein’s father. Gowtham is a billionaire, in which this fact makes the entire college be surprised that Sachein is the only son of a rich business tycoon, as Sachein always stays very simple and down to earth. Now Shalini feels bad, that if she proposes her love towards Sachein at this moment, then he might misunderstand that she decided to marry him after knowing that he is so rich and decides to stay calm. Sachein leaves to the Coimbatore International Airport in Coimbatore and Shalini also follows him. In the airport, Shalini could not control her emotions and proposes to Sachein. She also revealed that it is her ego that didn’t let her convey her love during the last thirty days. Sachein feels so happy and the couple are united.

Santosh’s life is dictated by his father, who decides everything for him. However, when Santosh falls in love with a girl, he struggles to convince his father to let him marry his girlfriend.

Ram is introduced to be an youngster who loves graffiti and doesn’t believe in everlasting love. He has gone through 9 loves in his life, and thinks that love between two people eventually dies out. As a person with strong morals, he is honest and wants to love life and live with open mind, open thought and open action with his lover. Jaanu (Genelia D’Souza) studies in the same college as Ram. He falls in love with her at first sight and goes onto wooing her. She eventually ends up falling for him, but wants him to promise to love her forever. Ram, of course, nonchalantly dismisses this and explains how he cannot love her forever. This leads to a clash of their ideologies. Ram shows Jaanu how even true love stales after a while and true love cannot stay forever, while Jaanu shows him examples of everlasting love, like her friends and her parents. However he makes it clear that love between two people is never the same as it first is. Ram doesn’t really bother about feelings of Jaanu and assumes that things work out for him with her because of how he feels for her without genuinely caring about how she feels and wants her future. Ram shows narcissism in most parts of the story.

Gautham (Bharath), a college dropout and good-for-nothing guy, falls in love with Narmada (Genelia D’Souza), the daughter of a local don Sakthivel (Radha Ravi). She lives in a hostel after learning that her father is a criminal who now wants her to marry his partner Sardar’s (Brahmaji) brother. So the two lovers elope to Mumbai, and they are soon tracked and separated. Finally, Gautham, along with his friends, fights against all odds to win back Narmada.