The reason Japanese castles are considered distinctive is that they differ from Chinese and Western castles.
Specifically, the difference lies in their defensive focus; Chinese castles generally concentrate their defenses on the city walls.
Because large numbers of commoners often live inside Chinese cities, and in times of chaos, those outside the walls will desperately run into the city, by Chinese tradition, the garrison has a duty to protect the people, so most of the defending force is positioned on the walls, with added structures like barbicans, horse-face towers, and sheep-walls to enhance the walls' defensive capabilities and functions. Sometimes, to protect the walls, soldiers are even sent out to fight with their backs to the wall.
At the same time, if the city wall falls, both the military and civilians usually lose all their will to fight, shouting "The city is breached!" and fleeing in all directions, thus completely declaring defeat.
