On Filiel's 15th birthday, she received her mother's necklace as a memento from her obstinate astronomer father. Her common and tedious life was turned into a life of conspiracies. With her new life, many adventures await. (Source: ANN)

On a sunny afternoon in her Paris apartment, assassin-for-hire Mireille Bouquet receives a strange email from Kirika Yuumura, a young student from Japan, inviting her to make a pilgrimage to the past together. Initially thinking the email is nonsense, she changes her mind when it begins playing a song that she recognizes from her youth. Upon first meeting each other in person, the two are suddenly ambushed by gun-wielding men. While Mireille is capable of fending off the assault, she discovers that Kirika is quite adept in combat situations after she takes out several gunmen on her own. Despite her proficiency at killing, Kirika laments her inability to feel remorse for her victims. In addition, Kirika apparently has no memory of how she came to acquire the skills she possesses or even of her real identity. Sensing shared history between them, Mireille agrees to team up with Kirika, and together, they embark on a journey to uncover the mysteries of their pasts. Operating under the codename Noir, the duo's fragile alliance is tested as they begin accepting jobs, each one bringing them closer to the truth of who they really are.

Koyomi Araragi has recently survived a vampire attack and met several girls plagued by supernatural entities. On top of all this, he wakes up one morning to find himself kidnapped and tied up by his girlfriend Hitagi Senjougahara. Araragi's sister Karen has run afoul of Deishuu Kaiki, a swindler who once conned Senjougahara's family. As a result, Senjougahara has imprisoned Araragi to keep him safe from the devious Kaiki. But when Araragi receives a frantic message from Karen, he sets out to rescue her. Along with Karen's troubles, Tsukihi, Araragi's other server, faces issues of her own. And when two mysterious women step into their lives, not even Araragi can anticipate their true goals, nor the catastrophic truths about his family soon to be revealed.

October 4 marks the fateful day when a high school girl vanished, triggering an unpredictable series of events. In order to unravel the mystery behind the girl's disappearance, all of the key witnesses connected to the case recount the events leading up to and following the crime. As the pieces to the story come together, they all seem to be connected to one individual—taxi driver Hiroshi Odokawa.