The Other World's Books Depend on the Bean Counter, Vol. 2 (light novel) — Yatsuki Wakatsu

After getting accidentally summoned to another world, former office worker Seiichiro ends up becoming extremely close with the handsome knight commander Aresh -- although what exactly that means remains ambiguous, even after they begin living together. Just as that's happening, Seiichiro meets a priest who reminds him a bit of Aresh. When Aresh returns from his latest expedition, will he find a rival waiting for him?