Nobody mentions this one, but that's because you need to watch the main series first to feel its weight. Atsuko's investigation notes reframe everything you thought you understood about the dismemberments, turning her into the person who saw what everyone else missed. She's not solving the case from safety. She's walking into the dark the same way her brother does, except nobody's watching her back.

Mouryou no Hako Special is a one-episode side story to the main series, a mystery thriller with supernatural elements. It centers on Atsuko, the younger sister of lead character Akihiko Chuzenji, and presents the notes she kept while looking into the brutal dismemberment cases at the core of the main story, giving viewers a view of those events through her records.