"I studied at a Buddhist university in Tokyo, but I was very disappointed," Mr Hirosue said.
"All religions seemed rotten and hypocritical to me, because they were all polluted by earthly desires. Then, I visited one of Aum's communes. It was a very cold day, but the first man I encountered was wearing nothing but a cotton shirt and trousers, and no socks.
"I asked him if he felt cold, but he said he did not, because he had overcome all earthly desires."
Mr Hirosue was standing at the gate of the sect's grounds in the village of Kamiku-Isshiki, on the slopes of Mount Fuji, where traces of a compound associated with the making of the nerve gas sarin were found last year. He would not let us inside, but gave us a video entitled Slaughtered Lambs, which claims that the chemical traces were the result of attempts by the Japanese authorities to poison the cult's members.
According to the video, Mr Asahara's followers had witnessed military helicopters and jets spraying sarin on the group's communes. But the cult believes its war with the state began long ago.
The fear inspired by Aum Shinri Kyo was demonstrated by a friend in Tokyo who asked me not to discuss the cult in public. "You might be followed if someone overheard our conversation," he said. "You might be targeted next time."
In Kamiku-Isshiki, where the youthfulness of the sect's followers is striking, local people have reason to be nervous. Several villagers recalled occasions when members of Aum Shinri Kyo fled into their houses at night, in an attempt to escape.
"Their pursuers came right into the house and dragged them back," one man said. "We didn't have time to call the police." A farmer whose land borders an Aum commune said one follower had asked him to help him escape, but had added in the same breath that Princess Masako, wife of Crown Prince Naruhito, was a US spy.
The lunacy of the sect's beliefs - its followers expect to be the only survivors after the world comes to an end in 1997 - appeals to young people, alienated by the materialism that has accompanied Japan's economic success.
Aum Shinri Kyo promises its followers the spiritual benefits missing in prosperous Japan: a purposeful life in rustic communes and ecstasy through yoga meditation.
"You have a lot of people who want to realise their identity, make their life more fulfilling," said Professor Hiromi Shimada, an expert on new religious movements, at Nihon Women's University.
In 10 years, Aum Shinri Kyo won 10,000 adherents. It also has four overseas branches, including New York and Moscow, and uses Radio Moscow's airwaves. But other sects have grown faster. A nine-year-old group, Science of Happiness, regularly fills the 50,000-seat Tokyo Dome, for productions featuring its leader, Ryuho Okawa.
The new sects demand a level of devotion rarely seen in Japan's traditional denominations. Shoko Asahara on Tuesday urged believers in a radio broadcast issued from Vladivostok to be prepared for death.
Most Japanese consider themselves followers of both Buddhism and Shintoism, but few are regular worshippers.
Most converts are young, and many have lite backgrounds. Kuniyasu Take, of Doshisha Women's University, traced the popularity of the sects to a rigid educational system that leaves young people with a longing for "something totalitarian", adding: "Japanese are a people who rarely make decisions for themselves. We need more education in democracy."
Professor Take compared Mr Asahara to the ancient shamans of the Shinto religion, who won authority by claiming spiritual links to the gods. "The spiritual trend among young people today... is to seek immediate ecstasy, by-passing traditional organisations. Charismatic people like Shoko Asahara catch that tendency."