The Taishou era didn’t end in 15 years, but went on for another 25. In order to protect her waning family, a girl resolves to marry a man she doesn’t even know the name of. However, just before the marriage was to take place, the girl’s younger brother mysteriously committed suicide by self-immolation and was found holding an old book in his hands. Appearing before the bewildered young girl was the “Imperial Library Intelligence Asset Management Bureau,” more commonly referred to as “Fukurou.” According to these men, there exists “Maremono,” which are books that greatly affect their readers. On top of that, ever since the incident involving the girl’s younger brother, she unwittingly gains the ability to see “Auras” (the sentiments of the Maremono which manifest as bright lights and are usually invisible to humans). It was as though fate were trying to drag the young girl in its flames. And then, even though apprehensive, the girl chooses to venture outside her bird cage. Jealousy, hatred, scorn, compassion, and love. What awaited the girl was the darkness of betrayal that had already begun to bewitchingly inlay the imperial capital. Toyed by and swayed within that darkness, will the young girl finally reach the truth after her struggles, or…?

In a futuristic era, “The World” is a peace-bringing entity. Though no one knows its location, it has watched over Earth for so long that war has become merely a fable. The airship Norn’s task is to deliver nine ability users to The World.

After collecting the last person, Norn takes off. Included onboard are eight men and three women—Koharu, who has finally escaped her loneliness and detests her destructive power; Mikoto Kuga, born to a noble family, who uses her barrier skill to protect the Norn and those it carries; and Nanami Shiranui, whose ability only brings pain, and who wishes to die for a past sin she has committed. While en route, suspicions arise amongst the passengers when they realize there are too many people onboard.

As they try to determine who has snuck aboard, the ship is attacked by an unknown assailant aiming to stop the Norn’s progress at all costs. From this chaos arises questions: why were they granted powers, and what must they do once they reach The World?

Within Cardia Beckford’s hazy memories, she can recall her father Isaac and the home where she lives alone, feared as a monster by the townsfolk—for in her body, she carries a deadly substance. Embedded in her chest by her father, the eternally beating heart—also known as Horologium—has the capability to produce infinite power. However, it also makes her skin destroy anything it touches.

Many in London seek the Horologium, including the terrorist organization Twilight, with whom Isaac is rumored to have close ties. To obtain the Horologium’s power, the British military forces Cardia to leave her home as their prisoner. But on the road, she is whisked away by the gentleman thief Arsène Lupin, who says he will steal her heart. Joining Lupin and his companions, Cardia begins a journey to discover the truth behind Isaac’s connection with Twilight, her missing memories, and the Horologium within her chest.