Ririchiyo Shirakiin is the sheltered daughter of a renowned family. With her petite build and wealthy status, Ririchiyo has been a protected and dependent girl her entire life, but now she has decided to change all that. However, there is just one problem—the young girl has a sharp tongue she can't control, and terrible communication skills. With some help from a childhood friend, Ririchiyo takes up residence in Maison de Ayakashi, a secluded high-security apartment complex that, as the unsociable 15-year-old soon discovers, is home to a host of bizarre individuals. Furthermore, their quirky personalities are not the strangest things about them: each inhabitant of the Maison de Ayakashi, including Ririchiyo, is actually half-human, half-youkai. But Ririchiyo's troubles have only just begun. As a requirement of staying in her new home, she must be accompanied by a Secret Service agent. Ririchiyo's new partner, Soushi Miketsukami, is handsome, quiet... but ridiculously clingy and creepily submissive. With Soushi, her new supernatural neighbors, and the beginning of high school, Ririchiyo definitely seems to have a difficult path ahead of her.

Fifteen years ago, disaster struck human civilization, and now dangerous man-eating monsters roam the ravaged lands, posing an existential threat to the remaining survivors. Amid this turmoil, an isolated facility shelters children and nurtures them in peace. However, as a few among them find out about the world beyond the narrow periphery of their nursery's walls, their curiosity about it slowly grows. Meanwhile, in the outside world, young survivors Maru and Kiruko band together to search for a special place called Heaven, each for their own reasons. Carrying past burdens and tragic secrets, the two hope to find answers to the cruelty they have experienced in their lives and in the world, which still remains in tatters.

Yuu Izumi leads a high school life filled with one mishap after another. No matter how improbable the situation, unfortunate events strike him at every turn. In possession of such terrible luck, Izumi enters his second year with a single wish in mind—to spend more time with his affectionate girlfriend, Micchon Shikimori. Cute, athletic, and caring, Shikimori is immensely popular at their school. But since they began dating a year ago, Izumi has witnessed a surprising side to his otherwise adorable girlfriend: when the need arises, she turns incredibly cool! His misfortunes are easily avoided when she is there to protect him with an awe-inspiring look on her face. Charming in every way, she never ceases to make his heart skip a beat. Unfortunate as he may be, Izumi is sure to see his days of bad luck end thanks to the cute yet cool Shikimori.

Kazuya Kujou is a foreign student at Saint Marguerite Academy, a luxurious boarding school in the Southern European country of Sauville. Originally from Japan, his jet-black hair and dark brown eyes cause his peers to shun him and give him the nickname Black Reaper, based on a popular urban legend about the traveler who brings death in the spring. On a day like any other, Kujou visits the school's extravagant library in search of ghost stories. However, his focus soon changes as he becomes curious about a golden strand of hair on the stairs. The steps lead him to a large garden and a beautiful doll-like girl known as Victorique de Blois, whose complex and imaginative foresight allows her to predict their futures, now intertwined. With more mysteries quickly developing—including the appearance of a ghost ship and an alchemist with the power of transmutation—Victorique and Kujou, bound by fate and their unique skills, have no choice but to rely on each other.