Reincarnated Into a Game as the Hero's Friend: Running the Kingdom Behind the Scenes (Manga) Vol. 4

Saving the kingdom is hard enough even with his memories of playing the game in which the world is based on. But Werner von Zehrfeld must do it all without letting anyone know about his prescient knowledge. Cue his plans to hold a training drill nearby a fort that he knows will soon get attacked by the demons. With Mazel off on his adventure, it's the hero's best friend's time to (literally) hold down the fort!