Provided are, in the 5GS, a method and a communication mechanism for procedures of initial registration of a UE and a periodic or mobility-based registration for implementing management of information about network slice or non-public network function. Furthermore, provided are a method and a communication mechanism for a deregistration procedure after completion of the registration procedure. Furthermore, provided is a method for managing information about network slice in association with each procedure and state transition. Accordingly, provided is, in the 5GS, a communication mechanism for implementing a function related to management of information about network slice or non-public network function.