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.

This is a female rimuru of story where rimuru was born as a true dragon. She is the oldest and strongest of the true dragons and the big sister of Veldenava. One day she had to leave her brother and sister to go into hibernation but accidentally slept for a bit too long. When she wakes up, she finds that her brother had died and that her sister Velzard had to take the burden of raising the other two by herself. What will she do now that she is back ? Female rimuru OC