Setagaya family murder

In December 2000, a couple and their two kids were murdered in Setagaya in Tokyo. After killing the entire Miyazawa family in their house, the suspect remained at the scene for several hours. He used their toilet, ate their food, drank tea, used the family computer, and took a nap on their couch. Police uncovered the killer’s DNA and many specific clues about their identity, but the perpetrator has never been identified.