A ritual ceremony performed when a person changes his identity in the society and acquires new esponsibilites.
It is a declaration to outside about the personal change in a social sense. It is also a prayer for safe and peace to come with the change.
In ep.25 "Air", members of SEELE comment that the Human Complementation Plan is "the Rite of Passage aimed to bring new vigour to human which has become blocked-out".