Masami Tsuchiya was born on January 6, 1965, in Chiyoda, Tokyo, Japan. A highly intelligent and academically gifted individual, Tsuchiya pursued higher education at the prestigious University of Tsukuba, where he specialized in physical and organic chemistry. After earning his master's degree, he appeared destined for a promising career in science. However, a personal turning point would lead him down a dark and deadly path.

In 1991, following a car accident that left him with whiplash, Tsuchiya began attending yoga classes in search of physical relief. These sessions, however, were hosted by Aum Shinrikyo, a religious cult led by the self-styled guru Shoko Asahara. Captivated by the group's teachings and mysticism, Tsuchiya became deeply involved. At age 26, he formally joined the cult, abandoning any conventional career aspirations and immersing himself fully into the organization.

His deep loyalty to Asahara bordered on fanatical. Tsuchiya referred to the cult leader as sonshi, meaning "honorable master," and described himself as a “direct disciple of the guru.” He took up a central role in the group’s so-called “Ministry of Health,” which ironically had little to do with wellness and more to do with death. Leveraging his scientific background, Tsuchiya began synthesizing powerful chemicals and narcotics for the cult, including LSD, PCP, VX nerve agent, and most notoriously, sarin gas.

Masami Tsuchiya was one of the masterminds behind some of the deadliest terrorist acts in Japanese history, all under the banner of the doomsday cult Aum Shinrikyo. Though not the one who released the toxic substances, he was the chemical architect of death, the man responsible for creating the very weapons used to carry out the atrocities.

His crimes began to surface in 1994 when Aum Shinrikyo targeted residents of Matsumoto, Nagano. On June 27, cult members released sarin gas in a residential area, killing seven people and injuring hundreds more. This attack was a rehearsal for something far worse.

On March 20, 1995, the cult launched a coordinated chemical assault on the Tokyo subway system during the morning rush hour. Five members released liquid sarin gas on several trains, killing 12 people and injuring over 1,000. Tsuchiya was not among the operatives in the subway, but he was behind the production of the sarin itself. The chemical formula he refined was so potent and pure that prosecutors later described him as the second most important figure in the attack, outranked only by Shoko Asahara.

In addition to sarin, Tsuchiya also produced VX nerve agent, which was used in three known attacks between 1994 and 1995, resulting in one confirmed fatality. He also synthesized recreational and hallucinogenic drugs such as PCP and LSD, further demonstrating the breadth of his chemical arsenal. Authorities later determined that he had played a key role in housing other cult fugitives, although this specific charge was later dismissed in court.

Tsuchiya was arrested shortly after the 1995 subway attack, along with other top leaders of the cult. His trial began in Tokyo and gained national attention. Throughout the proceedings, he remained loyal to Asahara and often mocked prosecutors and observers in the courtroom. His defiance was as chilling as it was disturbing.

In January 2004, the Tokyo District Court found Tsuchiya guilty of six out of the seven charges, including his role in the Tokyo and Matsumoto sarin attacks and the VX gas killings. Although he had not personally executed the attacks, the court emphasized that his scientific contributions were essential to their success. The presiding judge labeled him as “sheer evil” and sentenced him to death.

Appeals followed but ultimately failed. The Tokyo High Court upheld the death sentence in August 2006. The Supreme Court of Japan finalized the decision in February 2011, stating that Tsuchiya played a decisive role in enabling Aum’s most lethal acts.

On July 6, 2018, Masami Tsuchiya was executed by hanging, along with cult leader Shoko Asahara and five other senior Aum members. In one of his last public statements, Tsuchiya acknowledged the court’s ruling and said it was a “natural result,” expressing a desire to offer a “lifelong apology” for his crimes.