Isekai Mokushiroku Mynoghra: Hametsu no Bunmei de Hajimeru Sekai Seifuku

Takuto Ira succumbed to illness at a young age and ended up reincarnating in a world that resembled the strategy simulation game, "Eternal Nations," which he loved playing when he was alive. What appeared in front of him was Atou, a girl belonging to the evil civilization that he used to play as, "Mynoghra." The two of them decided to create a new country in this world once again. (Source: Kadokawa, translated)