Kizuitara Musou Game no Akuyaku Shogun Datta Ken. Hametsu Route wa Buttsubusu

A man works in an exploitative company, and his only joy in life is playing the hack-and-slash game "Brave of Kingdom" when he gets home from work. But one day, when playing the game, he sees something strange, and the next thing he knows, he is inside the world of the game, with the familiar adjuta...

Source: MyAnimeList