It is the Edo period. Ichitarou, the young master of Nagasakiya, one of the largest stores in Nihonbashi, has been in poor health since birth and is unable to go out. However, Ichitarou is always protected by demons such as Shirasawa and Inugami, who serve him. One night, Ichitarou goes out secretly and witnesses a murder. From that day on, bizarre murders begin to occur one after another in Edo... With the help of the demons, Ichitarou's search for the culprit begins! (Source: Official site, translated)

After an accident sent her family to their deaths in the ocean, Hinako Yaotose keeps returning to the thought of sinking forever into the sea herself. With Miko Yashiro as her only friend, Hinako manages to keep up a semi-happy facade, but whenever Miko leaves her side, she slips into despair. Everything changes one summer when she meets a mysterious girl with eyes as deep and clear as the sea, drawing Hinako in like nothing else has in a long time. During her absent-minded search for the girl, Hinako is suddenly pulled underwater by a beastly deep-sea creature, only to awaken to the presence of the girl—Shiori Oumi—who takes on a monstrous form and kills Hinako's attacker. Despite this heroic act, Shiori's intentions are no different from any other monster's: she wants to eat Hinako. The following morning, Shiori walks into Hinako's class as a transfer student, and Hinako cannot help but smile—at last, someone who could fulfill her quiet wish for death has appeared before her.

When high school student Hinata Sunohara was summoned to another world to defeat the Demon Lord, he promised to marry Mariabelle, a beautiful dark elf. But once his mission ended, Hinata was returned to Earth, leaving Mariabelle devastated. After a month back in Japan, Hinata's life has seemingly gone back to normal. However, everything changes again when Mariabelle suddenly appears in his room! Swearing to remain by his side forever, she begins living with him. As her obsessive love grows by the day, Mariabelle wishes to protect Hinata from any threat and ensure that he only has eyes for her.

A human may become a vampire only if they fall in love with one—and 14-year-old Kou Yamori wishes for nothing more. Kou has decided to fall in love with a vampire named Nazuna Nanakusa, and he has only 10 months of nightly rendezvous left to realize his goal. Kou's friends, Mahiru Seki and Akira Asai, are slowly coming to terms with the existence of vampires and Kou's decision to become one. As Kou realizes that a woman close to Mahiru is a vampire, he is unsure whether to support this relationship. Meanwhile, Anko Uguisu, the human detective bent on killing vampires, closes in on Nazuna and her coven. When an encounter leaves one of the vampires seriously injured, they learn that their human memories hold the key to a weakness that can be their demise—and to protect Nazuna, Kou must find out about her past.