There is even a Baekje castle in Japan

Perhaps because the original form is somewhat well-preserved,
even though it is a mountain fortress built by an external power a long time ago, it seems to be included among Japan's 100 castles.
Kino Castle.
It is in Okayama, near Himeji and Osaka.
Located in the heart of Japanese history, it isn't very far when looking at the whole of Japan.
I heard there is a folktale depicting it as a monster, but it seems it was eventually
overthrown by the forces of the Japanese mainland.
The Baekje people lived quite deep into the country, not just on Kyushu island.
The rammed earth walls are still properly intact. It makes me want to visit it once.
(This is a screen capture from YouTuber Lee Pan-ro's video)