The investigation into the murders is among the largest in Japanese history, involving over 246,044 investigators who have collected over 12,545 pieces of evidence.[7] In 2015, it was reported that forty officers were assigned to the case full-time.[2] Every year, the Tokyo Metropolitan Police Department makes an annual pilgrimage to the house for memorial ceremonies.[8][9] In 2019, it was reported that thirty five officers are assigned to the case.[6]