Vishnu Vishal is a faint hearted, and a soft spoken guy, who pretty much fears everything. On the first day of his job he reunites with his long lost friend, and immediately become the best of friends. One day as he stands at the bus stop, he sees Catherine Tresa in her scooter, and immediately gets attracted to her. As he stands there mesmerised, she unexpectedly stops in front of him and offers him a lift. He of course readily accepts the ride and on the way to his office, he falls in love with her. 

A love stricken Vishnu Vishal opens up to Soori and asks him to help him figure out where Catherine lives. They both try their best, but to no avail. Then, co-incidentally, he ends up visiting Catherine's house, for official matters and that's when he realises that she lives right next to him. A visibaly delighted Vishnu Vishal from then onwards tries to woo her. 

After Catherine finally accepts him, she says that she has been in love with him way before he even saw her, and that's why she offered him a lift so that he would notice her. Vishnu Vishal gains more assurity about his relationship and goes to Catherine's house along with his family to respectfully ask her hand for an alliance. But his father becomes the villain and insults him, because he knows how much of a meek guy Vishnu Vishal is. He says that he will only get his daughter married to a "Man".  In the meanwhile he gets to know that he has a rare disease and decides to donate his kidney to Anandraj who plays an Arab sheikh. The rest of the plot revolves around whether he really donates his kidney, and what happens to his love of his life.

Kathanayagan is as predictable as it gets, solely based on a so called co-incidental twists and turns. The movie gains momentum, and is actually funny only with the second half of the movie; after Vijay Sethupathi's cameo, Anandraj and Rajendran's entry. Else, the movie forces a smile out of you here and there, but is as dry as ever. Vishnu Vishal, has stripped all his inhibitions and has delivered a good performance, he perfectly aced in comedy. Whereas Soori kept the viewers entertained with his top-notch dialogue delivery, while Catherine seemed to be in the movie just for glamour. 

Director Muruganandham has done a decent job, by making a simple and a breezy movie, with a lack of a serious story line. The main advantage for the film is that it, looks colourful and seems to be funny, though actually it could have been more funnier. Also bankrolled by Vishnu Vishal, the movie will be loved if the audiences watch it just for fun.

Up-and-coming musician Sean Roldan has scored the songs and the background for Kathanayagan, and has done a good job with it. Laxman's cinematography skills come to the fore and is on point, giving an added layer of a glossy look to the movie. 

In short, Kathanayagan, is a past-time.