The Other World's Books Depend on the Bean Counter (Light Novel), Vol. 1

Seiichirou Kondou is a 29-year-old accountant and major workaholic. When he's accidentally transported to another world, not only does he demand a job, he starts whipping the lackadaisical Royal Accounting Department into shape! But when he gets in over his head and nearly dies from overwork, the handsome Commander Aresh steps in to save him, and the two develop a unique, physical relationship...as a form of medical treatment?!