DISCLAIMER: This is just a product of creative imagination of mine... none of the characters and the events are mine, though I'll add some new events in between.

80 years have passed since Yuuki's defeat. Rimuru, after dwelling for countless years at the end of time and space, has surpassed Veldanava in terms of strength and is, therefore, the strongest being in the Cardinal world. With his strength, he easily dealt with the aftermath of the final battle and accomplished his dream of coexistence between monsters and humans. Although he is happy with the results, his daily routine consists of constant paperwork. During one of these boring days Ciel, who is worried about the mental state of her master, suggests creating an alternate Timeline and traveling back in time. Rimuru, not wanting to do everything over again, comes back with an alternative idea. Going back in time but with one addition: instead of traveling to his original time of reincarnation as a slime, he decides to go much further in time and become one of the ancient demon lords.

Rimuru, after successfully repelling Velgrynd, the catastrophic dragon, takes his well-earned break. But, unfortunately, his break gets cut short after Guy had called in for Walpurgis. While preparing for his departure, Rimuru gets attacked when he crosses the teleportation space made by Guy's subordinates. When he comes to, he finds out that he has been brought back to Japan. Albeit, a different Japan from what he knew. This is a crossover between two of my favorite Anime's. This one will be a continuing series just like my first Fanfiction. Stay tuned for more!