When Kimizuka witnesses a plane hijacking, he becomes the sidekick of the detective who stops it.

Nagisa Natsunagi, inspired by her transplant heart, meets Kimizuka; Kimizuka gets information from an unexpected source.

Kimizuka and Natsunagi take on detective responsibilities; Yui Saikawa asks them to protect a sapphire, but there is something bigger at stake.

Kimizuka and Natsunagi try their best to protect Yui Saikawa who is performing a stadium show. However, the two start to suspect that the idol has been hiding some secrets.

Siesta and Kimizuka investigate a series of murders by Cerberus, who steals victims' hearts. Kimizuka gets disappointed with Siesta's desperate tactic to pursue Cerberus.

Siesta injures her leg in the sudden battle against SPES's top executive, Hel. While Siesta recovers, Kimizuka meets a mysterious girl in the back alley.