After the king and his eldest son die, the kingdom of Landor is left without a ruler. Asta--last surviving member of the royal family--stands in line for the throne. However, before he can claim it, he must fulfill a quest: find the legendary "Key to the Kingdom." Both ancient beasts and a variety of contenders--including a princess, a dimwitted military captain, and a villainous aristocrat--imperil his journey. Someone will find the Key, but will it be Asta?