Realist Maou ni Yoru Seiiki naki Isekai Kaihaku (Light Novel)

In a rotted away castle, Ashta awoke as a Demon King. With his wisdom from a past life, he would rule over his lands as a thorough realist. “Demon King, why are you attacking the level 1 Heroes?” “Defeat them before they become stronger. That is called strategy.” “Demon King, why are you sending fake money to the enemy country?” “To bring chaos to their economy so they will self-destruct.” “The werewolf troops have attacked. Should we use silver bullets?” “Not bullets, shoot them with canons.” And like that, Ashta ‘reformed’ the old tendencies. He became a lord who was loved by the people and his subordinates and would go on to be called the most powerful Demon King in history.