Other name: Kaibutsu Oujo, Kaibutsu Ohjo, Monster Princess, 怪物王女
Hiyorimi Hiro has just moved to the city to meet his sister. Since their parents died, he and his sister Sawawa have lived apart. Now, Sawawa has gotten a new job as the caretaker of a creepy old mansion, and has sent Hiro a letter asking him to come and stay there with her. While walking down the street, he saves a young woman clad in Gothic clothes from being crushed by construction beams, but ends up losing his own life in the process.
The girl then resurrects him, leaving him alive in the hospital morgue. He wakes up confused over what happened, only to encounter the woman again as she eliminates some wolf creatures. She addresses Hiro as her servant and introduces herself as Hime (Japanese for "Princess") and explains that she is a member of the royal family of the Monster Realm.
All members of the royal family are endowed with the power to turn a dead body into an immortal warrior, who will serve and protect them, and become semi-immortal. Hiro is now Hime's immortal warrior, but she herself is not immortal yet, which is why she needs help from warriors. The story then follows Hiro as he assists Hime in killing creatures that have been sent by her siblings to attack her in the competition for theMonster Kingdom's throne.