Mouryou no Hako: Chuuzenji Atsuko no Jikenbo - Hako no Yurei no Koto
Genres: Mystery, Supernatural, Suspense
Type: Special, Episodes: 1
Aired: May 22, 2009
Studio: Madhouse
Source: Novel
Rating: R - 17+ (violence & profanity)
Synopsis:
A side story that reveals the investigative notes that Atsuko, the younger sister of the main character Akihiko Chuzenji, wrote about the brutal dismembering incidents in the main story.

(Source: ANN)