On April 28, 2021, 21 year old college student Momona Yoshioka was found severely injured in her apartment. She had multiple stab wounds to her body and head injuries inflicted with a crowbar, and the apartment was covered in blood. She was taken to the hospital but later died from her injuries.
Her neighbor, 48 year old Satoru Kamoto, was found dead in a fire in his apartment below hers. Investigators determined he deliberately set the fire and was also Momona’s attacker. His fingerprints were found on the weapons, and witnesses saw him climbing between apartments using a ladder.
In the weeks leading up to the attack, Satoru had become increasingly fixated on Momona’s apartment above him. He was known to be extremely sensitive to noise and had previously confronted another neighbor about minor sounds. This extreme sensitivity to noise is believed to have played a central role in his obsession with Momona.
Evidence showed the crime was premeditated. Satoru had blocked Momona’s door, searched online for rope ladder and kerosene, and purchased these items shortly before the attack.