The fifth instalment of the Boukyaku Tantei Series.

With her resignation letter tucked into her breast pocket, Inspector Hatopa was shaken. Her last case is a drowned body found floating in a park fountain. However, due to its inexplicability, she is forced to investigate in cooperation with the famous forgetful detective, Okitegami Kyouko...... A detective wishing to quit and a workaholic detective. A strange tag team takes on the mystery!

(Source: Kodansha, translated)