Kimizuka, a middle-school student, meets the beautiful detective siesta in the process of thwarting a plane hijacking. As they investigate a mystery at Kimizuka's school Cultural Festival, Siesta urges Kimizuka to become her sidekick.
A brief flashback featuring Siesta and Kimihiko from three years before the start of the story is shown. - Fubi talks to Kimihiko about him "restarting" his detective career.
Siesta, Kimizuka, and Char join forces to rescue Alicia from Hel and SPES, but are taken aback by a series of shocking revelations that make them question everything they thought they knew about the organization.
On the night of Yui's big stadium show, Kimizuka and Natsunagi struggle to protect her from a hidden assailant. But the further the two dig into the plot against Yui, the clearer it becomes that the teen idol has secrets of her own.
After taking a risk to stop Hel and her mutated terror-beast, Siesta pays a price for her courage which temporarily halts the fight against SPES while a surprising discovery is made by Kimizuka in an alley.
A teen idol, Yui Saikawa, enlists Kimizuka and Natsunagi--who has taken up the mantle of legendary detective--to guard a priceless sapphire. In preparing for this, the two realize that more than just a precious jewel is at risk.
Siesta and Kimizuka team up to investigate a string of murders committed by Cerberus, a heart-stealer, but as Cerberus escapes Siesta, she devises a risky plan that worries Kimizuka.
Alicia and Kimizuka search for the Eye of Sapphire while Siesta is recovering, and the three celebrate upon Siesta's recovery with an unexpected outcome.
Siesta and Kimizuka partner up to fight a constantly shifting enemy, but after the battle, the survivors are left with unresolved questions and must seek closure within their group.