Mathapoo' is a heartwarming and sweet romance that revolves around Karthik, a young man who moves from Madurai to Chennai and falls in love with Pooja, a beautiful and sweet young girl who helps him out. Karthik wanted to marry Pooja but, despite her family's approval, Pooja mysteriously rejects the offer. The reason behind the refusal is that she was taken to the police station after her male friends tried to date rape her and her mother blamed her for the fiasco. So, she had decided never to marry just to prove to her mother that she was blameless. But she continues to stick to her stand even after her mom realized her mistake and and wants her to marry Karthik.