Kaiko sareta Ankoku Heishi (30-dai) no Slow na Second Life

For more than 30 years, Dariel has been a loyal soldier in the Demon King's army, having been raised by Granverza, one of the Four Heavenly Generals. However, as Dariel lacks any magical potential, he is nothing but a disgrace in the eyes of Granverza's son, Bashubaza, who fires Dariel right after assuming his father's position as a general. Stripped of a home and a job, Dariel wanders the forests, where he stumbles upon a human girl named Marika running from a monster. After Dariel intervenes to help Marika, she invites him to stay at her village in return. There, he discovers that the reason he has zero suitability for magic as a demon is that he is, in fact, a human. However, Dariel is no ordinary human. Possessing potential that far outweighs even heroes, Dariel may soon find himself involved in the humans and demons' seemingly never-ending conflict, facing against the race he once considered allies. The dark soldier, Dariel (30 years old), who cant use magic despite being in the Demon Lords army, was fired for his lack of capacity. Having been raised by the previous Demon Lord himself, he finds that his adoptive brother, the new Demon Lord, has little use for him. However, after rescuing a village girl from a forest monster, Dariel is invited into her village and starts realizing that he may be considerably more powerful than what he thought...