"I wanted the others to talk more about what they did as lessons for anti-terrorism measures in this country, and I wanted the authorities and experts to learn more from them", she told a televised news conference.
Kamikawa, however, declined to comment on how the seven were selected among the death row inmates.
Asahara, who founded Aum Shinrikyo in 1987, was captured two months after the attack in one of the cult's buildings.
Some people argue that Aum Shinrikyo and spinoff cults remain unsafe, so its imprisoned members should be kept alive and grilled for information.
Shoko Asahara was one of 13 cult members waiting for the final result of pending verdicts and is the first to be executed by hanging for the 1995 attack, as well as the murder of the Sakamoto family and production of a chemical weapon.
Yuji Ogawara, who heads a lawyers' group against the death penalty at the Japan Federation of Bar Associations, said the executions do not bring closure to Aum's crimes. The attack, which failed, used a refrigerator truck to release the gas and a wind dispersed it in a residential neighbourhood, killing eight and injuring hundreds.
Tomomasa Nakagawa, a doctor also executed Friday, and several other cultists broke into the Sakamotos' apartment late at night, strangled them to death and buried them in the mountains.
"When I think of those who died because of them, it was a pity (my husband's) parents and my parents could not hear the news of this execution", she said. Executions are carried out suddenly with little warning to the condemned or their families when the day arrives, following a conviction and appeals process that can stretch out for years, as it did with Asahara.
The top Japanese government spokesman confirmed Asahara's execution but wouldn't comment on the others.
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The strategically placed canisters allow divers to stay underwater longer during the five-hour trip to reach the stranded team. Oxygen levels have dropped significantly inside the Tham Luang cave due to the high volume of rescuers passing through.
Asahara had been on death row for masterminding a 1995 sarin gas attack on the Tokyo subways and other crimes. The cult's founder was charged with planning the subway attack and other crimes that led to the deaths of 29 people. On February 27, 2004, he was sentenced to death by hanging.
The trials against the cult members only wrapped up in January this year after the Supreme Court upheld the verdict against one member sentenced to life in prison.
Asahara left school at 19 after qualifying as an acupuncturist.
He "lured young people, who felt a sense of emptiness in Japanese society", she said. "Now, I can pay a visit to her grave and tell her of this".
According to Japan News (The Yomiuri Shimbun), "These cases, which symbolize crime in the Heisei era, must be resolved before the era comes to a close." .
It is thought that it had 10,000 followers at its peak and the group gained official status as a religious organisation in Japan just two years after it was formed.
On May 16, 1995, the police corps investigated the headquarters of Aum Shinrikyo.
The police and the Public Security Intelligence Agency are gathering intelligence and closely monitoring followers who could possibly attempt to retrieve the bodies of Asahara and the six others.