Venturing into the wilderness, the skeptical Ryouta Murakami and the ambitious Kuroneko were on a quest to prove the existence of extraterrestrial life when a tragic accident occurred, reaping Kuroneko of her life and leaving Ryouta in a critically injured state. Ten years have passed since the disaster, and Ryouta is now living a normal life in high school. He vows to prove that aliens are real in honor of his late friend. A transfer student named Neko Kuroha unexpectedly arrives one day, bearing a striking resemblance to the late Kuroneko—even sharing a similar name. Most mysteriously, she seems to possess supernatural powers. As Ryouta takes more interest in Neko, he is drawn into a deadly world where dangerous scientists hunt magic-wielding witches that have escaped from their secret research laboratory. Neko is one of these escapees, but there are many others who are in similar situations, and it's up to Ryouta to protect them from their would-be captors.

To the unsuspecting eye Maki, Reimi and Yuka may not look like ace crime fighters, which might explain why they're stuck on traffic patrol instead of more "exciting" police duties. All that changes when Yuka gets herself kidnapped by a white slave organization run by a politically connected businessman who's got the rest of the police cowed. Now it's up to Maki and Reimi to don skin-tight battle armor, liberate a tank, and make sure that a certain slaver learns that when you play with fire, you're going to get your ass burned!

At the behest of her father, Yui Komori goes to live in a secluded mansion, home to the six Sakamaki brothers—Shuu, Reiji, Ayato, Kanato, Laito, and Subaru—a family of vampires. Though at first the siblings are confused as to why the girl has arrived, they soon realize that she is to be their new "sacrificial bride," not to mention their other, more carnal intentions for her. After meeting the brothers, Yui quickly begins to question why her father would have sent her here and why she feels a strange, new pain in her chest. With each brother more sadistic than the last, Yui's life as a captive takes a harrowing turn in her new home. As her days turn into endless nights, and each brother vows to make her his own, Yui falls deeper and deeper into madness and ecstasy.

Yui Komori, still held captive by the Sakamaki brothers—pureblood vampires after her blood—experiences yet more bizarre twists to her life following her stay at their household. Though haunted by enigmatic dreams, Yui soon deciphers their meaning when caught in a car crash, which subsequently leads to meeting four new vampires: the Mukami brothers, Ruki, Azusa, Kou, and Yuuma, who themselves capture the bewildered girl. Yui later awakens in the Mukami mansion, where the brothers reveal their plans for her: she is their "Eve," and her blood will find the "Adam" among them; together, they will have the power to rule the world. However, with the Sakamaki brothers hot on their heels, things might not go quite as smoothly as they had imagined.