Kaibutsu kun

The king of the Kaibutsu or Monster Kingdom thrust his son, young prince Taro, into the human world. Prince Taro, also known as Kaibutsu-kun, must live among people for a while as part of a grooming process before taking over the kingdom. So begins the sometimes scary, sometimes touching and often hilarious adventures of Kaibutsu-kun and his three affable attendants, Dracula, Wolfman and Franken. The monsters meet humans Hiroshi and his older sister Utako, and through them, they learn about friendship, love, family and ultimately, the purpose of their mission: what it takes to be a leader.
(Source: DramaWiki)
~~ Adapted from the manga "The Monster Kid" (怪物くん) by the writing duo Fujiko Fujio (藤子 不二雄).