Askr Yggdrasil's Wood

Exiled to a desolate and harsh planet, Ayr spends his days hunting giant monsters as his food source. Then, everything changes when a police officer comes and tells him his exile was revoked. After arriving in Askr he learns that a lot of time has passed while he was gone. 100 years. Everything seems to be different now, but one question remains: For what reason was his exile revoked after this long time? (Source: MangaDex)