The Other World's Books Depend on the Bean Counter, book 1
Yatsuki Wakatsu et Kikka Oohashi2019

One day, twenty-nine-year-old accountant Seiichirou Kondou is accidentally transported to another world. As compensation, the Romany Kingdom promises to take care of all his living expenses, but the workaholic Seiichirou still asks for a job. Once he's placed in the Royal Accounting Department, he starts whipping his lackadaisical colleagues 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?!

Titre original : Isekai no Sata wa Shachiku Shidai, book 1 (2019)