Tokyo residents who lived through the chaos and horror of nerve gas being released on the city's subway lines during rush hour on March 20, 1995, have expressed relief tinged with concern after the execution of Shoko Asahara on Friday morning.
A Japanese government spokesman confirmed Asahara's death and said six other members of Aum Shinrikyo had also been executed.
Japan's public broadcaster NHK said six other former members of the cult who had been convicted of involvement in the attack had also been hanged shortly after Asahara, whose real name was Chizuo Matsumoto.
The BBC explained that it took such a long time for Asahara's execution to take place because in Japan, no one may be executed until every accused person and accomplice has been tried, had their appeals heard, and been sentenced.
Atsushi Sakahara, who was injured in the attack, welcomed the executions.
Despite the horror that persists over the Aum's subway attack and other crimes, some experts had warned against the execution of Asahara and his acolytes.
Amnesty International lamented the executions, saying that these failed to deliver justice and is "the ultimate denial of human rights".
Kamikawa said that capital punishment is "unavoidable" for such heinous crimes. Asahara was 63 years old. "I hope they will not launch terror attacks", like the 1994 sarin gas attack in Matsumoto, Nagano Prefecture that killed eight people.
Chief Cabinet Secretary Yoshihide Suga said only that the Justice Ministry would make an announcement later Friday.More news: Pipeline outages: Nigerian oil output takes a plunge
Twelve other members of Aum Shinrikyo were sentenced to death for their roles in the Tokyo attack. However, ultimately, the death penalty was given to Shoko Asahara and others high in the chain of this organization.
Cult guru Shoko Asahara, left, of Aum Shinrikyo walks with Yoshihiro Inoue, then a close aid, in Tokyo.
Shoko Asahara, head of the Aum Shinri Kyo group, masterminded the sarin gas attack on rush-hour commuters on March 20, 1995. His death sentence was finalized in 2006.
Aleph, a successor group to Aum Shinrikyo, is still involved in a court case over settlements to the victims of the 1995 and other attacks.
It is extremely complex to label the religious fundamentals of Aum Shinrikyo.
"I've been in pain for years", he told AFP.
Cult members have said they believed Asahara's prophesy that an apocalypse was coming and they alone would survive it.
Japanese authorities said they were on alert for potential retaliation after the executions and local media reported police were visiting groups linked to the Aum and successor cults.
At its peak, the cult had at least 10,000 members in Japan and overseas, including graduates of some of Japan's most elite universities.