Kuro no Senki II: Isekai Teni Shita Boku ga Saikyou nano wa Bed no Ue dake no You desu

On the day of his high school entrance exam, a boy named Crono is suddenly transported to another world. He became the commander of the demi-human army, won many great victories, and is feted as a lord. He gathers beautiful women one after another... A royal-road war story with battles, domestic politics, and sex! (Source: Kadokawa, translated) Note: Starts from Chapter 9 of the prequel, with a new version of Chapter 10 and 11.