The story takes place in Japan. The year is 2030 and Earth has been completely overrun by a viral disease named "Gibia" that turns infected people into various different monsters, based on their age, sex, and race. A samurai and a ninja from the early Edo period travel together through time and arrive in a ruined Japan to aid a professor working on a cure for the virus. Together, they fight countless Gibia monsters, outlaws, and other fierce foes on their journey to save mankind.

After leaving her idol career behind, Fuuka Miyazawa finds herself on a spontaneous flight to Okinawa instead of returning home to her pity party in Morioka. Bearing a heavy heart and nowhere to go, she aimlessly wanders around the area until she stumbles upon Gama Gama Aquarium—an aging aquarium on the verge of closing down. With a lack of visitors and costly but necessary repairs needed to keep its doors open, the director is faced with shutting down the establishment for good by the end of the summer. The director's aquatic life-loving granddaughter—Kukuru Misakino—cannot stand the thought of the aquarium closing and is determined to make enough money by the end of the season to keep the doors open. Seeing the unique magic of the aquarium, Fuuka begs Kukuru for a job; however, she soon finds that her lack of experience makes her more of a hindrance than anything else. At the same time, Kukuru realizes that her ambitious goal might be more than she can handle. With mounting pressure from all around them, will Kukuru and Fuuka be able to save the one place they hold close to their hearts?

In a world of magic and monsters, Krylancelo Finrandi and his foster sister Azalie Cait-Sith were once promising students of sorcery, prodigies at the famous Tower of Fangs. But an experiment gone horribly wrong warps Azalie's appearance, trapping her in the form of a dragon. Elders at the Tower—more interested in preserving their reputation rather than their students' lives—drive off the transformed Azalie and cover up the incident. Outraged, Krylancelo strikes out on his own, taking the new name of "Orphen" and vowing to return Azalie to her normal state. Five years later, Orphen's quest has stalled. A chance encounter brings him face to face with Azalie again, but he still has no way to restore her body. And with a hostile group of sorcerers hunting her down, he may be running out of time. The past and present collide as Orphen tries to find how to save Azalie from their former teachers and friends.