Goshujinsama wa Yamaneko-hime

Goshujinsama wa Yamaneko-hime (ご主人様は山猫姫) is a light novel series by Ayumu Kasuga with illustrations by Kazuyuki Takami.

Plot
Seirin is the only outcast of an Elite Family. With great effort, He barely able to get into work as a tutor of a foreign princess for... the last princess of Shimuru main branch family. Mine is still an innocent 13 years old princess, a graceful lady─ or maybe not. Doesn't like being selfish and rampaging super problematic child. While Seirin is having a headache, he kind of want Mine to be princess like.

Also somehow, Princess Hime is being attached to Seirin as a teacher. But, The Empire who supposed to have signed a peace treaty with Shimuru has declared a war. It become a dilemma for Seirin, could it be a big step to become a Hero!?