The body was bound with adhesive tape over the mouth and hands, and pantyhose over the legs, and the neck was stabbed with a sharp blade, so the police ruled it a murder case.
Based on the circumstances of the crime scene and the fact that Junko's father's slippers seemed to have been worn, it was thought to be the work of a known acquaintance of the victim.
[7] In September 2006, ten years after the incident, it was disclosed that both legs had been tied in a special method known as a "karage knot" and that DNA from a non-family member was found in matchbox residue left at the scene.
Firefighters found the victim on the second floor and immediately took her to the hospital, where she was pronounced dead on arrival due to blood loss from stabbing.
Investigators determined Junko Kobayashi had been dead before the fire started, due to lack of smoke particles in her lungs.
Karage knots are used in landscaping, scaffolding, kimono dressing, stage costumes, waste paper collection, electrical work and civil engineering.
A match from a Buddhist altar was used to set fire to a wardrobe in a 6-mat Japanese-style room on the east side of the first floor.