Kim Jongin is a genius scientist. He is only a 12 years old and a lonely, parentless kid. As miracle as it sounds, Jongin created a robot called D.O. D.O. is too perfect to be called a robot. It's figure is too humanlike. He thought D.O was a perfect invention but, it is still lacking in one thing called 'Heart'. Years passes, he still could not programmed heart in D.O., until the day his life was taken from him, leaving the heartless D.O. alone.