35 year old bachelor Jehan and his partner in crime Priyantha try to exploit the loopholes in the law in order to make a living.Koombiyo tells the story of Jehan Fernando, who has neither family nor home and lives alone in an abandoned building complex in Colombo. He accidentally meets Hiruni and Priyantha Mahaulpathagama in a public bus when Priyantha is coming to Colombo on his search for a job. Jehan convinces Priyantha to abandon the job he is going for and join Jehan's company Purchasing Lanka instead, which delivers retail items to customers claiming they are from supermarkets when in reality they are bought from the local flea markets. Priyantha starts living with Jehan while being a partner in his business and they quickly become good friends.

In this tale of deception and misadventure, a group of five village con men, each with unique skills, form a traveling performance troupe to camouflage their illicit actives. When approached by Swami, a con artist posing as a Hindu priest, they agree to pose as fake businessmen in a scheme to buy two Walampooris.