The thirteenth instalment of the Boukyaku Tantei Series.

When Kyouko-san's powers of deduction are taken away, her partner, Yakusuke, is on the run!
How will she take on the series' greatest enemy? A time limit mystery!

"The characters on the ceiling. It was I who wrote them."

A young man, Yakusuke, has been deemed a suspect in an attempted murder case. As usual, he asks the forgetful detective, Okitegami Kyouko, to solve the case. However, in the middle of the case, Kyouko-san is shot. She survives but loses her great deduction ability. In pursuit of the culprit, Yakusuke is confronted by someone who knows about the forgetful detective's past...

(Source: Kodansha, translated)