Isekai Office Worker: The Other World's Books Depend on the Bean Counter

When ordinary salaryman Seiichirou Kondou sees a girl struggling on his way home from work, he doesn't think twice about going to help her. Unfortunately for him, however, the girl, Yua Shiraishi, was in the midst of being summoned to another world, and Seiichirou gets pulled along with her. The people of the fantasy kingdom don't quite know what to do with this unexpected interloper, and are stunned (and put off) by Seiichirou's insistence on working for his keep. But because he's not the summoned saint, Seiichirou has no defenses against the natural "magicules" that fill the air, and he finds himself on the brink of death. The only thing that can save him is an infusion of magicules, administered repeatedly over time, to acclimate him. And somehow, handsome young knight Aresh Indolark ends up being the one to give it to him.

Synopsis from Anime News Network