Yuusha no Kawari ni Maou Toubatsu shitara Tegara wo Yokodori Saremashita

As a member of the hero's party, Arga hid his identity and was on a journey to subjugate the Demon King with the hero. At last the party cornered the demon king, and Arga brought him down. However, the hero insists that he was the one who killed the Demon King, and then falsely charges Arga with a crime and banishes him from the Imperial Palace. The warrior who devoted his life to the hero as a part of his corp would walk a new life in a strange town in the countryside.

(Source: Kadokawa, translated)