The film stars Arulnidhi and Ineya, while John Vijay, Madhusudhan Rao, Uma Riyaz Khan, Krishnamoorthy, and Balakrishnan play supporting roles.

Mouna Guru illustrates a misunderstood college youth who becomes unwittingly involved in a crime plot that spirals his life out of order.

As a result, he is unable to control his anger and ends up with trouble due to his unpredictable behavior, which becomes a constant worry for his mother and brother.

Despite scoring high marks in school, he joins a local arts college in the city and stays in a hostel, where trouble begins.

Meanwhile, ACP Marimuthu, Inspector Rajendran, SI Selvam, and HC Perumalsamy witness a car accident in the outskirts of Chennai.

One day, a bag containing all the stolen items is kept in Karuna's hostel room, making him as the prime suspect of all the threats, which leads him to get arrested.

They forge a story that Karuna is suffering from a mental disorder which makes him think that he is being chased by a group of policemen for a fake encounter.

However, Karuna gets enraged and kills Marimuthu, Rajendran, Selvam, and Perumalsamy, where he is sentenced to psychological treatment (as he is falsely believed to have a mental disorder).

The Hindu gave the film a positive review citing that "Mouna Guru is one of the small gems of Tamil cinema this year" and that "it marks a promising debut for Shantakumar and advances Arulnidhi's career".

[10] Behindwoods.com gave the film three stars out of five praising the director Shantakumar's execution, while also singling out John Vijay's act as "the performance of his career".