My Captain Mr. Underground.

A notorious grave robber Dae-chool, recently stole a precious Buddha statue. However, two kids Ji-min and Byung-oh steal it from him for fun. Dae-Chool tricks the kids telling them that he is a special agent from the Ministry of National Treasures, and persuades the kids to help him "in the cause of justice". As they experience one mishap after another, the kids and Dae-chool form a family-like relationship.