Muhyo & Roji's Bureau of Supernatural Investigation

Muhyo and Roji visit the home of Shiratori Aya, a client who says a black shadow has been playing her piano at 2:00 AM every night. Muhyo concludes that the shadow is a vengeful spirit born from countless people who envy Aya's talent, but in fact... Later, a package arrives at the bureau for Roji, containing a "magic-sealing pen" and an invitation to take an exam for a promotion to first-class secretary. Then Nana enters with a photo she took of a spirit on a pedestrian bridge...