Princess Seraphina of Astria becomes the Demon Lord who will destroy the world and is killed by Cassiel Rune Ertman, the successor of the Holy Kingdom. When she opens her eyes, she returns to being a peaceful 10-year-old with her beloved family alive before the destruction of the world? In front of Seraphina, who is looking for a way to eliminate the Demon Lord's seed in order to live peacefully with her family, Cassiel, who killed her before her return, appears as a suitor...?! (Source: Kakaopage, translated)