Charles wants to catch hold of Karthiga and make her understand his love for her. Shaffiq needs Karthiga to get back the smuggled diamonds that he had entrusted with her. Meanwhile, Karthiga witnesses a murder at her deserted office and the killers are after her.

Inidhu Inidhu depicts the happy college days of a group of undergraduate students. Freshmen Siddhu (Adith), Aravind alias Tyson (Narayan), Vimal (Vimal), Shankar (Shravan), Madhu (Reshmi), Aparna aka Appu and Jiya join an upmarket college in the city. Each of them comes from different states of the country. They are ragged by the seniors at the college which makes them bond with each other. Eventually, Siddhu falls for Madhu, Tyson falls for his senior Sravanthi, fashionably called Shravs (Sonia), who is not receptive. The rest of the film is how the four couples get closer during their four-year course, peppered with pangs of jealousy, separated, reconciliation before going their separate ways upon graduation.