Akuninmenshita B-kyuu Boukensha: Shujinkou to Sono Osananajimitachi no Papa ni Naru

Gray, a B-level adventurer, is a mob character in the RPG Bright Fantasy.
Or that was the way it was supposed to be.......

But when Gray saves an orphan from thugs on the road by chance, he decides to take him in and care for him as a father figure. That orphan turns out to be "Iska" — the Hero of the story.

His choice will change the fate of this world.

(Source: ComicWalker, translated)