B-Rank Adventurer with a Scary Face Becomes a Father for the Hero and His Friends Volume 1 (manga)

Gray, the B-rank adventurer, was a background character in the RPG known as Bright Fantasy ...or at least that's what he thought. After saving orphans from being attacked by goons, he resolves to provide for them as a father. But one of the orphans is Iska, the other world's future hero, and his choice will greatly change its destiny.