While the definition of "new religion" varies among scholars and religious groups, the term is generally used for groups founded sometime between the mid-19th century, when Japan started modernizing, and the mid-1970s. Religious groups founded after the 1970s, such as Kofuku-no-kagaku (Institute for Research in Human Happiness), are sometimes referred to as "new-new religions."
Many religions founded before the war were persecuted by authorities during the war and prewar years, a period in which state Shintoism was pushed. In the postwar years, however, new sects have emerged in abundance.
While many of them enshrine either Buddhist figures or Shinto gods, they usually have unique doctrines that differ from traditional religions and are tailored to fit the needs of modern-day followers.
Aside from certain antisocial cults, most maintain respect for traditional religions and enjoy relatively good relations with them, experts say.
While some lasted only a short time, others expanded rapidly along with the country's robust postwar economic growth.
Nobutaka Inoue, professor of religious studies at Kokugakuin University, said 10 percent of Japanese either belong to a new religion or have learned about them through seminars or published material.
"The situation is that everybody in this country has at least one member of a new religion among his or her close relatives," he claimed.
He said new religious groups are successful because they provide city dwellers with a spiritual base they lost when they left their hometowns and the traditional temples and shrines of their youth.
"New religious groups substituted traditional religious affiliations (represented by temples and shrines), which traditionally served a geographical community with fixed members, through the nation's urbanization phase," he said.
But Inoue believes the decline in young converts to new sects reflects the current social changes, including the rapid development of information technology.
"Information technology enables people to pick up specific doctrines or lessons they like online, and people no longer seem to feel they need a specific religion," he said.
Despite the drop in young adherents, Inoue believes young people are becoming increasingly interested in religions and spirituality, as reflected by the emergence of Aum Shinrikyo and other fanatical groups and the increasing fascination with occultism and the supernatural.