Kyun! Ho Gaya Na' is a romantic comedy - a simple story about love and life. Diya Malhotra's father decides that she should travel to Mumbai to help his friend Raj Chauhan run a small orphanage. Diva (Aishwarya Rai)nwill stay at the home of the Khannas, who also are friends of her father. Diva then meets Arjun Khanna (Vivek Oberoi), a seemingly free-spirited, fun-loving, adventurous guy. The two soon realize, however, that they will be staying in the same house since the Khannas, her father's friends, are Arjun's parents. The friendship that develops between Diya and Arjun and their opposing views on love and marriage are at the heart of this film.