A situational romantic comedy, Kyun! Ho Gaya Na is a simple story about love and life.
Diya Malhotra (Aishwarya Rai) is a young and intelligent university student. She was brought up in Coorg single-handedly by her father. Diya spent most of her time playing with the kids at her Uncle's (Amitabh Bachchan) orphanage. Diya travels to Mumbai for her exams. While there, she stays with her father's friend Mr Khanna, and meets their jovial prankster son, Arjun (Vivek Oberoi). Diya and Arjun have completely opposing views on love and life. Over the time their friendship blossoms. Diya professes her love to Arjun, who breaks her heart unaware of the fact that he is in love with her. A heartbroken Diya goes back to Coorg. One he realises he is in love, Arjun ventures off to the orphanage, in hopes of bringing Diya back.