Yoshihiro Inoue was born on December 28, 1969, in Ukyō-ku, Kyoto, Japan. As a child, he was deeply introspective and gravitated toward documentary films, often focused on societal problems such as poverty and animal cruelty. Despite his intellectual curiosity, his home life was emotionally strained. His father was stern, and family conflicts were common. His mother reportedly attempted suicide during his youth, creating an unstable and painful environment that Inoue would later attempt to escape through spiritual pursuits.

During high school, he studied martial arts, yoga, and the teachings of Agon Shu. In 1986, he attended a seminar hosted by Aum Shinrikyo, which was then known as Aum Shinzen no Kai. There, he met Shoko Asahara and was immediately drawn to him, describing the cult leader as the “ideal parent” he never had. His admiration for Asahara quickly evolved into devotion. Inoue appeared with other Aum members on national television in 1988, representing the younger generation’s growing interest in alternative religions.

After graduating from Rakunan High School in March 1988, Inoue planned to become a monk. His parents, reluctant at first, eventually agreed after negotiations with Asahara. Inoue briefly entered the Faculty of Law at Nippon Bunka University, but under Asahara's direction, he dropped out within his first year. He then took monastic vows and became a full-time Aum priest. His mother, too, joined the cult as a lay follower, solidifying the family's deep entanglement with the group.

By 1989, Inoue had risen quickly through the ranks of Aum Shinrikyo. He was awarded the title of Grand Master after allegedly achieving Kundalini Yoga. He became one of the organization’s most trusted operatives and was known for his knowledge of surveillance and wiretapping, skills he reportedly learned from a private detective. Throughout the early 1990s, he was involved in several of the cult's most sinister activities, including kidnapping, chemical experimentation, and covert assassinations. Within the Aum hierarchy, he was eventually promoted to “Shogo Guru,” a high-level status

Inoue’s direct involvement in multiple crimes began well before the Tokyo subway attack. As one of Aum’s top strategists, he was implicated in numerous violent incidents including the murder of dissidents, coordinated chemical attacks, and the intimidation or elimination of perceived enemies.

He was especially connected to the 1995 Tokyo subway sarin gas attack, which resulted in 13 deaths and thousands of injuries. Inoue coordinated the operation as its general commander, managing logistics and ensuring the chemicals were distributed simultaneously across the city’s busy subway lines. Although he did not release the gas himself, his role was instrumental in executing the event.

Inoue was also involved in the Tokyo Metropolitan Government parcel bombing, the cyanide gas attempt in Shinjuku Station, and the chemical death of a notary public's office manager. In total, his actions and coordination within the cult contributed to one of the worst domestic terror campaigns in modern Japanese history.

His arrest came on May 15, 1995, during a routine police check in Akiruno City. When asked for identification, he initially cooperated, revealing his real name. Authorities were stunned, as he was already on Japan’s most wanted list. He was found in possession of materials linked to the government parcel bombing, solidifying his ties to ongoing terror plots.

Following his arrest, Inoue sent a message to fellow cult members urging them to leave Aum Shinrikyo. He expressed regret for his past and began to publicly distance himself from Asahara. However, his sincerity was widely questioned, both by investigators and fellow members. During trial, he appeared remorseful, but often minimized his role or deflected blame, claiming he had been manipulated by others within the cult.

The Tokyo District Court initially sentenced him to life in prison on June 6, 2000, sparking controversy given the prosecution’s demand for the death penalty. This marked the first Aum-related case where the court denied capital punishment. However, as testimonies from other cult members began to mount, particularly regarding Inoue's enthusiasm and leadership in the sarin attack, the prosecution appealed.

On May 28, 2004, the Tokyo High Court overturned the earlier verdict, sentencing him to death for his role in the arrest, confinement, and death of the notary public manager, and for serving as a general coordinator in the mass murder during the subway attack. His appeals were ultimately dismissed, and the death sentence was confirmed in 2010.

In prison, Inoue remained at odds with other Aum members, particularly Tomomitsu Niimi and Kazuya Takahashi, over who was more responsible for various crimes. His claims often changed and contradicted earlier testimony, including statements about the source of chemicals and who led specific operations. He also sent letters to victims' families, some claiming that others were responsible for the deaths, shifting blame even in his final years.

Despite filing a motion for retrial just months before his death, the request was denied. On July 6, 2018, Inoue was executed by hanging at the Osaka Detention Center. He was 48 years old.

His final words were short and cryptic:

“First of all… good.” 

His body was cremated and returned to his parents.