Convicted for his participation in the Sakamoto family murder and several other crimes, Hayakawa was executed on July 6, 2018, at Fukuoka Detention House.

In 1990, after the campaign for election of Aum Shinrikyo turned into a fiasco, this cult group decided to overthrow the government of Japan by force.

To get access to the technical documents of military equipment, he presented some high-performance computers to Moscow Institute of Physics and Technology.

[5][6] As the deputy leader[1] of Aum Shinrikyo, Hayakawa arrived in Western Australia in April 1994, and then purchased an area of nearly 2000 square kilometers known as the Banjawarn Station.

[7] According to media reports from 1995, sheep carcasses in Banjawarn showed signs of exposure to sarin, the substance used in the Tokyo subway attack.