In the middle of the night, Indhiran (Vishal), accompanied by his two friends, Sathish (Jagan) and Karuna (Sunder Ramu), purchases a gun illegally from a local gangster. Back home, Indhiran stares at his wishlist and recalls his past.
Since childhood, Indhiran has been suffering from narcolepsy, a rare disorder, which makes him fall asleep whenever his emotions reach an extreme and hinders him from living an ordinary life. He needs to be accompanied all the time, companies hesitate to hire him, although he has excelled in academics, and he cannot impregnate women since he would fall asleep during sex. However, he can still hear whatever is being said when he is sleeping.
Indhiran creates a list with 10 goals he wants to achieve on his own. One day, he ventures out alone, which was one of his goals. When he is almost hit by a vehicle while crossing the road, his fear mounts and he falls asleep in the middle of the road. A passerby (Mayilsamy) makes him pose as an orphaned corpse and gathers money from onlookers for his burial. Meera (Lakshmi Menon), who passes by, takes pity and shells out almost five grands.
She later meets Indhiran in a mall and falls unconscious, seeing him alive. After clearing up the misunderstanding, they start dating and fall for each other.Meera makes one of the dreams of Indhiran come true (i.e.)getting a kiss from a beautiful woman by kissing him. But Meera's father opposes their marriage as Indhiran cannot give birth to a child. Meera urges Indhiran to find a way how he could stay awake. It dawns on Indhiran that he had never fallen asleep while taking a shower. Believing that her father will accept Indhiran only when his potency is proved, Meera and Indhiran have sex underwater in their pool, resulting in Meera becoming pregnant.
On a late night drive, Meera and Indhiran find themselves in an under-construction bridge. Their car is hit by another and the shock makes Indhiran doze. Meera is brutally attacked by four thugs. Indhiran can hear the entire incident but remains asleep. Meera falls into coma and her baby has been aborted. A heartbroken Indhiran vows to exact revenge on the perpetrators.
The narrative moves back to the present. Deciding to venge all by himself, Indhiran fails to testify to the police. To safeguard himself from any sudden shock, he buys a portable audio player and uses it with full volume. Enquiring Meera's friends, Indhiran first suspects Karthik (Rishi), a rich but ill-mannered guy, whose marriage proposal was rejected by Meera. Indhiran confronts him, but he feigns ignorance about the incident.
Indhiran remembers that it were four persons, with one of them named Sekhar, and Sekhar's ringtone, while the police finds out that the offenders rode a red car. Indhiran stumbles upon a red car in a petrol bunk and enquires the driver who claims that the car was with a mechanic named Sekhar on the day the crime took place. At the workshop, he spots the mechanic who tries to abscond, recognising Indhiran, and a chase ensues leading them to a building under construction. Informed by Sathish, Karuna arrives there and kills Sekhar. He then slits himself and is admitted for treatment. Karuna then recollects.
Married to Karuna for two years, Kavitha (Iniya) was dissatisfied with her drunkard husband; she begins an affair with Aravind, a rich friend of Karuna. He spends a lot of money on buying her expensive gifts. Indhiran gains knowledge of this and advises Kavitha against it. It turns out that Karuna, to realise his ambitions of running a business in US, had been using his wife to manipulate Aravind. Citing Indhiran's confrontation, Kavitha bluffed to Aravind that if Karuna gets to know about the affair, he would kill them both. She suggested that the only way to solve it once and for all is to arrange the amount of ₹ 20 million Karuna needs to settle in the states. With him gone, they could enjoy being together. Aravind agreed to finance Karuna out of his lust for her.
Later, when Karuna and Kavitha are celebrating their success, Indhiran drops by unexpectedly. They mess up; Indhiran suspects them and informs Aravind who confronts the couple. When Aravind realizes that he had been cheated, he hits Kavitha in a fit of rage and she dies. Infuriated, Karuna retaliated and kills Aravind. Karuna arranges for disposing them with the help of the thugs and lies to Indhiran that Kavitha has eloped with Aravind. Since he assumed that Indhiran was responsible for the death of Kavitha, Karuna had planned to take revenge by making him suffer the same way and requested the thugs to rape Indhiran's girlfriend, Meera.
The remaining thugs insist Karuna to bring Indhiran to the same place where Sekhar was killed. Finding out that it was Karuna who had killed Sekhar, they beat him up. The thugs then remove the audio player from Indhiran who gets an adrenaline rush and dozes off. While the thugs are assaulting him, one of them breaks a water pump which splashes water all over and awakens Indhiran. He kills them all and finally Karuna too. Indhiran tells that he had seen Karuna killing Sekhar but had come with him only to locate the other thugs.
With all his wishes fulfilled, he has a new wish that he would make Meera recover soon. The final scene shows Indhiran hugging Meera who is tearful hearing him which shows that she is definitely recovering.Vishal as IndhiranLakshmi Menon as MeeraIniya as KavithaSaranya Ponvannan as SumathiJayaprakash as Meera's fatherSunder Ramu as KarunaPrinz Nithik as GunaJagan as SathishRishi as KarthikMayilsamy as PasserbyV. I. S. JayapalanPyramid NatarajanAarthi as PeriyanayakiNisha KrishnanShyamili SukumarChethan Cheenu
Vishal announced that director Thiru would direct a film under his production house in June 2013, and that Jai would play the lead role in the film. However, in October 2013, Jai announced that his schedules were busy and thus Vishal himself opted to play the lead role in the film. Lakshmi Menon was selected to play the lead heroine.
The film began production on 29 November 2013 and it was announced that Iniya was added to the cast to play another leading female role.
STAR Vijay bought the satellite rights. Telugu dubbed version Indrudu released on 20 June 2014.
The Soundtrack album was composed by G. V. Prakash Kumar.
All lyrics written by Na. Muthukumar.
The film opened to positive reviews from critics many praising vishal's performance, screenplay, fast-paced narration while criticizing its second half which was vulgar part of the film.
Baradwaj Rangan of The Hindu wrote, "The hero is a narcoleptic, and this aspect is not just a cool marketing gimmick. It has been integrated into the very fibre of the film...The first half is strong..the director, Thiru, displays a lot of control in scenes that could have erupted into melodrama....And then we enter the second half, and the film goes haywire...Still, given the general state of hero-oriented Tamil cinema, where a hollow kind of masculinity is endlessly celebrated, it’s nice to root for a hero who isn’t a slacker but a brilliant student, and who sits down with his pals for a cup of tea, rather than booze, and who gets rejected by a girl his mother sets him up with". Sify stated, "Thiru is able to make an engrossing actor driven entertainer without any super hero gimmicks. Naan Sigappu Manithan is an gripping entertainer which is not run-of-the-mill". Siddarth Srinivas of Cinemalead gave 3.5/5 and concluded, "Vishal sleeps, you wont!" The Times of India gave it 3/5 and wrote, "There is intelligence in this script...but Thiru slips quite a bit in the second half as he goes for one twist too many in explaining why Meera is attacked. What we are left with is a feeling of mild discontent, as a promising premise is compromised for a generic revenge drama". Rediff gave 3/5 and stated, "Naan Sigappu Manithan is a riveting revenge drama with an honest narrative, excellent performances and many entertaining twists and turns". OneIndia rated the film 3/5 and called it an "edge-of-the-seat entertainer" and a "perfect commercial film for all classes". Anupama Subramanian of the Deccan Chronicle gave 3/5 and wrote, "Overall, a gripping entertainer with an unusual theme.". Indiaglitz gave 2.75/5 and concluded, "A fair entertainer that loses the steam through the second half.". Behindwoods gave it 2.75/5 stars and stated, "Despite minor moments where the script deviates from its USP, Naan Sigappu Manithan pulls through as a pretty tense drama that ticks the commercial requirements". IANS gave 2.5/5 and wrote, "NSM stands testimonial to the fact that a simple story that has been milked dry over the years can still be narrated in myriad engaging ways. One such way is what we see in this film, which is not an exceptional thriller, but definitely has the potential to keep you hooked." Hindustan Times gave 2/5 and stated, "Despite a novel subject, Naan Sigappu Manithan fails to deliver". Bharath Vijaykumar of Moviecrow gave 2.75/5 and concluded, "NSM has a neat first half and a decent second half with disconnect between the two halves.".
The film opened magnificent response at the box office by collecting ₹12.14 crore in its first day. The film grossed ₹30.1 crore in its first weekend despite having competition from Tenaliraman (film).The film grossed ₹3.52 crore in chennai first week. According to traders, the film grossed ₹70 crore worldwide in its final collection.The film declared 'Super-Hit' at the box office.The film became a hat-trick hit for Vishal as well as Thiru.