Career
He was Aum"s "minister of internal affairs". Judge Yujiro Nakatani said that his Aum-related crimes began in 1989 with the strangulation killing of Shuji Taguchi, who had attempted to flee from the cult. He also strangled Tsutsumi Sakamoto and Tatsuhiko, his 1-year-old son the same year.
Before the Tokyo subway gas attack, Asahara wanted to try the sarin gas on humans.
All was going well until the device sprung a leak, splashing liquid sarin onto Tomomitsu Niimi, Asahara"s security chief "Fortunatly" for Niimi, Kiyohide Hayakawa was present and quickly administered an antidote in time to prevent Niimi"s nervous system from shutting down.
Together with Ikuo Hayashi, Niimi participated in the subway gas attack (there were several other perpetrators as well): Hayashi delivered the sarin-filled package and pierced it with a sharpened umbrella tip, while Niimi served as a car driver. Unlike other former Aum members involved in criminal acts, Niimi delivered no apologies and stoically accepted the death sentence.
He then spoke about human sufferings, saying that "some are suffering thinking that this world is illusory and some thinking that it is realium
Concerning the former members who now testify against their guru who did them so much good, I believe their suffering is based on the perceptions that this world is real".