The Key To The Kingdom

a new series debuts from renowned fantasy manga artist kyoko shitou! after a king and his eldest son die, the kingdom of laudere is left without a ruler. asta, the last surviving member of the royal family, stands in line for the throne. but 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?source: https://www.mangaupdates.com/series/q9kawc2/oukoku-no-kagi