The ancient Demon Lord Rimuru

More than 200 years have passed since the war between the Empire and the victory over Ivarage. Rimuru is currently sitting in his office, bored out of his mind. His loyal partner Ciel sees his situation and gets an idea that can solve Rimuru's boredom. Come along on your journey as Rimuru travels over 20,000 years into the past to become an ancient demon lord.