During a thwarted plane hijacking, middle schooler Kimizuka encounters the striking detective, Siesta. Soon after, as they delve into a mystery surrounding Kimizuka's school Culture Festival, Siesta proposes that he become her partner.

Kimizuka is approached by Nagisa Natsunagi, a girl whose longing seems born from the very heart she received in transplant. Seeking assistance, Kimizuka turns to Fuubi, who leads them to a most unexpected acquaintance, one who offers surpri…

Yui Saikawa, a celebrated teenager, sought the protection of Kimizuka and Natsunagi—the latter having recently assumed the role of a legendary detective—for a priceless sapphire. As they prepared for the task, both men understood that the t…

The night of Yui Saikawa's major stadium performance saw Kimizuka and Natsunagi desperately trying to shield her from a concealed threat. Yet, with each layer of the conspiracy against Saikawa they uncovered, it became increasingly evident …

Siesta and Kimizuka are investigating a string of murders committed by a figure known only as Cerberus, a killer who, for some dark purpose, steals his victims' hearts. As Cerberus continues to evade Siesta's relentless pursuit, she conceiv…

Siesta gambles everything to intercept Hel and her monstrous creation, and her bravery exacts a heavy toll. The confrontation brings the struggle against SPES to an immediate standstill, if only for now. Amidst the aftermath of the conflict…

As Siesta recuperates, Alicia assumes the mantle of temporary investigator, pursuing the Eye of Sapphire with Kimizuka's help. Upon Siesta's eventual recovery, the trio celebrates; however, their rejoicing takes a surprising turn.

Recovered from his ordeal, Siesta is eager to continue the hunt for the serial killer and SPES. Yet, Alicia is determined to remain involved, and their differing approaches ignite a friction that sharpens the enigma surrounding her true ide…

Driven by the need to save Alicia, Siesta, Kimizuka, and Char ventured to confront Hel and SPES within their own domain. There, a series of unsettling revelations unfolded, leading them to a disturbing understanding: SPES concealed a profou…

A cruise brought Saikawa, Natsunagi, and Kimizuka together, but the voyage took an unforeseen turn when Kimizuka unexpectedly crossed paths with someone from their past. It soon became clear that a valuable object was aboard the vessel, dra…

With Natsunagi's life hanging in the balance, Kimizuka confronts Chameleon and discovers he is not fighting alone; aid arrives from unforeseen sources. Yet, against this cunning adversary, Kimizuka's companions—and his own inner strength—ar…

The echoes of Siesta resonated anew as it joined forces with Kimizuka in a desperate struggle against a relentless and adaptable enemy. Following this conflict, the survivors were burdened with lingering questions and uncertainties, compell…