The Other World's Books Depend on the Bean Counter (Light Novel) Series by Yatsuki Wakatsu, Wakatsu Yatsuki

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?!

Seiichirou, a typical corporate slave, was mistakenly summoned to another world alongside a Holy Maiden. He met the handsome young knight, Aresh, and they began a physical relationship by necessity. However, over time they've become more like true lovers. Unable to face Aresh's deepening feelings, Seiichirou throws himself into his work. He's been appointed as a guide for a delegation led by a foreign kingdom's third prince... moreSeiichirou, a typical corporate slave, was mistakenly summoned to another world alongside a Holy Maiden. He met the handsome young knight, Aresh, and they began a physical relationship by necessity. However, over time they've become more like true lovers. Unable to face Aresh's deepening feelings, Seiichirou throws himself into his work. He's been appointed as a guide for a delegation led by a foreign kingdom's third prince. Just before the welcome party, the outfit Aresh prepared for Seiichirou sparks a huge argument. Days pass without reconciliation, and suddenly Aresh is approached with marriage talks! At the same time, the research team completes preparations for the magic spell to send Seiichirou and Yua back to Japan. What will the two of them choose to do less