Reym, a seasoned adventurer, awakens to find himself living his seventh life, having retained the memories and skills from his previous six incarnations. Each of his past lives ended in tragedy, culminating in his death at the hands of the monstrous princess, Liscia, a feared and feral beast of immense power. This time, however, he is determined to alter his fate. Rather than fight or flee from the princess, he chooses an unprecedented path: he will tame and marry her. The story begins as Reym, now a young man in a frontier town, actively seeks out Liscia, who is still a wild and isolated child, barely surviving in the wilderness. He takes her in, not as a ward, but as his future bride, using his accumulated knowledge of combat, magic, and monster ecology to earn her trust and begin the arduous process of socializing and raising her.

The core of the narrative follows the decades-spanning journey of Reym and Liscia. Reym’s goal is twofold: to prevent Liscia from becoming the calamitous monster she was destined to be, and to create a peaceful life for them both. He acts as her teacher, protector, and eventual husband, guiding her through the prejudices of a world that fears her kind. The setting is a classic fantasy world with kingdoms, dungeons, and various humanoid races, where monsters are generally seen as mindless threats. However, Liscia’s existence as a "monster princess" hints at a more complex origin, possibly tied to ancient bloodlines or curses, which Reym must uncover.

The major narrative arcs chart their evolving relationship. Early arcs focus on survival and bonding, as Reym uses his past-life knowledge to procure food, shelter, and magical artifacts to help Liscia control her volatile power. A significant middle arc involves their integration into human society, where they face suspicion, political machinations, and attacks from those who see Liscia as a weapon or a demon to be slain. Reym often has to balance his pragmatic, future-savvy mindset with the emotional needs of his bride, who gradually develops human-like feelings and intelligence. Later arcs delve into the larger conflict of the world, as Reym’s actions begin to change the timeline, drawing the attention of the very forces—be they kingdoms, deities, or other monsters—that orchestrated his past deaths. He must confront the root cause of Liscia’s monstrous nature and the repeating cycle of his own reincarnation, all while protecting the family he has built across multiple lifetimes.