There are two types of Gates ; Permanent Gates and Temporary Gates.
Those Gates may be used by any Yōkai at any time unless they are Locked Down or Sealed.
Since it is quite exhausting to keep those Gates open - though a more powerful Deity might find it less tiring - they usually don't last any longer than a couple of hours at most.
Any Yōkai can use the Gate to come and go between the two Worlds.
The Gate is closed and sealed with a magic that can only be dispelled using the Crown.