Dec 30, 2000
Nighttime home invasion and murders
Between 11:30 p.m. and 12:05 a.m., an intruder killed the four family members inside their home.
View sequence of events
late night
Assailant likely entered via second‑floor bathroom window adjacent to Soshigaya Park.
around midnight
Rei was strangled in his bedroom.
around midnight
Mikio confronted the intruder; he was fatally stabbed with a sashimi knife, whose blade partially broke.
around midnight
Yasuko and Niina were attacked with the broken knife and then a household santoku knife.
Dec 31, 2000
Intruder remains in the house for hours
The killer stayed inside, used the computer and bathroom, ate food, treated injuries, ransacked rooms, and left clothing and other items.
View sequence of events
01:18–01:23
Family computer connected to the internet.
overnight
Consumed barley tea, melon, and ice cream; used first‑aid items and restroom without flushing.
overnight
Ransacked drawers; some cash taken; numerous items left behind (e.g., hip bag, clothing, knives).
Dec 31, 2000
Bodies discovered by Yasuko’s mother
At 10:40 a.m., Haruko entered the home and found the four victims, prompting a major TMPD investigation.
View sequence of events
10:40
Haruko enters the house and discovers the four victims inside the residence.
shortly after
Police are notified and the residence is treated as a major homicide scene.
same morning
The discovery fixes the final known endpoint of the overnight attack and begins the long-running TMPD special investigation.
Jan 1, 2001
Dietary trace evidence reported
Analysis of fecal matter left at the scene indicated the suspect had eaten string beans and sesame seeds.
View sequence of events
Forensic examination of fecal matter left at the scene identifies partially digested string beans and sesame seeds.
after testing
The finding reinforces the conclusion that the offender remained in the house long enough to eat and use the bathroom after the murders.
Dietary trace evidence becomes one of several unusual behavioral clues used to characterize the offender's post-crime conduct.
Jan 1, 2010
Statute‑of‑limitations reform
Japan abolished the statute of limitations for crimes eligible for the death penalty; the Setagaya case was widely cited in public debate.
View sequence of events
Japan abolishes the statute of limitations for crimes punishable by death, including the most serious homicides.
public debate
The Setagaya murders are widely cited as an example of why families and investigators opposed time limits on such cases.
after reform
The legal change ensures that prosecution in a case like Setagaya would no longer expire with the passage of time.
Jan 1, 2013
3D model of residence produced for investigation
TMPD used 3D printing to create a model of the house to support investigative reconstruction.
View sequence of events
TMPD uses 3D printing to create a physical model of the Miyazawa residence.
investigative use
The model helps investigators visualize internal movement, entry points, and the spatial relationship between rooms.
The project reflects the case's shift toward long-horizon reconstruction techniques rather than only fresh witness leads.
Jan 1, 2019
Police announce plan to demolish deteriorating house
TMPD stated the residence would be torn down due to structural concerns, noting evidence had been preserved.
View sequence of events
Police announce that the deteriorating residence is planned for demolition because of structural and site-management concerns.
same period
TMPD emphasizes that investigative evidence and documentation from the scene have already been preserved.
after public response
Family members and supporters push back, and the site remains symbolically important to the case's public memory.
Dec 1, 2021
Reward increased to ¥20 million
Authorities announced a reward of up to ¥20 million for information leading to the killer’s arrest.
View sequence of events
Authorities announce that the reward for information leading to an arrest rises to as much as 20 million yen.
reward structure
The total reflects a combination of public program funds and additional cooperative contributions tied to the investigation.
public outreach
The increase is meant to generate new tips in a case where abundant forensic traces still had not yielded a public identification.
Dec 17, 2021
Knife purchaser ruled out via DNA
TMPD reported a person of interest who bought the same knife model was visually identified but excluded after DNA comparison.
View sequence of events
Investigators develop a lead to a person who purchased the same knife model believed relevant to the case.
follow-up review
Enhanced imaging and investigative reconstruction make the purchaser seem worth closer scrutiny.
after DNA comparison
The lead is ultimately ruled out when the person's DNA does not match the biological material recovered from the scene.
Dec 9, 2023
Public appeals at Seijōgakuen‑mae Station
TMPD conducted a flyer campaign at Seijōgakuen‑mae Station to solicit information on the case.
View sequence of events
TMPD officers distribute flyers at Seijogakuen-mae Station as part of a renewed public appeal campaign.
same campaign
The outreach highlights the suspect's retained clothing and bag items as continuing identification anchors.
The event shows that decades later the investigation still relies on public recognition of physical evidence and memories near the area.
May 27, 2024
Setagaya Ward motion on DNA usage
The Setagaya Ward Assembly passed a motion promoting broader investigative use of DNA evidence in Tokyo.
View sequence of events
The Setagaya Ward Assembly passes a motion encouraging broader use of DNA evidence in investigations.
policy framing
The motion reflects continued local frustration that strong biological evidence in the Setagaya case had still not produced an identification.
after passage
The resolution is framed as support for expanding how DNA information can be used in Tokyo policing and cold-case work.