On December 30, 2000, the Miyazawa family in Setagaya Ward, Tokyo, were brutally murdered in their home. The killer remained inside the house afterward, used the victims' food and facilities, left extensive biological evidence and personal items, yet could not be identified in any domestic or international database.
Investigators preserved the evidence and pursued multiple theories—random intruder, targeted attack, or outsider—but despite DNA and forensic leads the case remains unsolved and the motive unknown.