Sect Shinto is not a movement, a school, or a family of related bodies. It is a legal category, created by the Japanese state in 1882 to hold the religious organisations it needed to distinguish from the shrine system it was building.
The reasoning was as follows. Having decided that shrine observance was a non-religious national duty owed by everyone, the government had to do something with the organisations that plainly were religions in the ordinary sense: bodies with founders, revelations, doctrines, scriptures, congregations and formal membership, which had grown up in the late Tokugawa and early Meiji years around charismatic teachers, mountain worship, purification practice and faith healing. So it separated them out. Six groups were made independent in 1882, and the number reached thirteen by 1912.
They include Kurozumikyo, founded by Kurozumi Munetada; Konkokyo, founded by Konko Daijin; Tenrikyo, founded by the peasant woman Nakayama Miki, whose revelations began in 1838; Misogikyo; Izumo-taishakyo; Fuso-kyo and Jikko-kyo, both built around the worship of Mount Fuji; Ontake-kyo, around Mount Ontake; and others. The published lists of the thirteen differ from one another in one place, which is a fair indication of how administrative the category always was.
What these bodies have in common is chiefly that they were not shrines.
The state also had a practical motive. An organisation with a founder, a doctrine and a membership roll can be registered, supervised and, if necessary, suppressed: and bodies of this kind were, Oomoto most severely, in the 1920s and 1930s.