These Japanese hilltop fortresses are really interesting. They look totally weird (and frankly, not that serious) to an eye used to Western medieval castles. But they have their own strengths. The sort of scattered design, where there's gaps between the strongpoints, lets them use terrain that might not work for a centralized medieval castle. And while it might mean individual bits can be defeated in detail, trying to use the spaces between to mount attacks would open the attackers to crossfire, and taking one part leaves most of the puzzle still intact, unlike a Western castle where usually one big breakthrough is close to the end.
That said, IMO a Western medieval siege train would cream one of these things.