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 takes an extreme risk to stop Hel and her mutated terror-beast, and pays a price for her courage. The outcome halts the fight against SPES, at least temporarily. In the wake of this battle, Kimizuka makes a surprising discovery in an alley.

Saikawa, Natsunagi, and Kimizuka set off on a cruise together, during which Kimizuka unexpectedly encounters a former acquaintance. It turns out that something precious is onboard the ship, something which attracts the wrong sort of attention.

Facing off against Chameleon with Natsunagi’s life on the line, Kimizuka finds that he is not alone in this battle, with help coming in unexpected forms. But against this wily foe, Kimizuka’s allies--and his own resilience--are tested to the limits.