The roof of the keep is red. Tsurugajo is the only castle in the country with a keep tiled in red. Under that roof, about a thousand cherry trees fill the grounds. Most are Somei-yoshino. Some are Yae-zakura, the double-flowered kind, which come later and darker.

So the range of colour on the ground is wider than at most castle parks, running from near-white to a deep pink, and all of it sits below a roof that is neither. The prefecture gives the flowering as the middle to the end of April.

Cherry trees at a castle are not unusual in Japan. Almost every surviving keep has them, and almost every ruined one has them too, planted where the buildings used to be. What is different here is the colour above the flowers rather than the flowers themselves. You notice it before you have decided what you are looking at.

Look up through the branches and the red comes through in pieces, in whatever gaps the white leaves open. Late in the afternoon the tiles deepen and the flowers, by contrast, go paler than they were at noon. When the petals fall they gather on the water of the moat and along the tops of the stone walls, and the line they make along the top of the stonework traces the shape of the fortress more plainly than the stones do on their own. It lasts a few days, and then the wind takes it.