Kaibutsu-kun, also called Monster Kid or Tarou Kaibutsu, is the prince of Monster Land. Ordered by his father, the King, he travels to the human world with his companions Dracula, Wolfman, and Franken for ascetic training. This journey prepares him for his future succession to the throne of Monster Land.

In the human realm, Kaibutsu-kun and his group face battles against various monsters, chiefly assassins from the demonic organization Demonish. These conflicts are central to his experiences away from home. His companions possess distinct characteristics: Dracula replaces human blood with tomato juice and frequently uses "damasu" in his speech; Wolfman acts as the group's housekeeper and cook, ending his sentences with "gansu"; Franken boasts immense size and strength but limited intellect.

From Monster Land, Kaibutsu-kun's father, the King, observes his son's development. The prince's training involves navigating challenges presented by adversaries like Prince Demokin, leader of the demons. His journey focuses on confronting these threats and fulfilling the training objectives mandated by the Monster Land monarchy.