Well, seeing as how I know nothing about Japanese trees, I'll use context clues.
Cherry is known as a relatively poor bowwood, weak in tension and moderate in compression, but when one holds together it is "an unusually sweet and fast shooting bow" to quote Tim Baker.
However, Japanese cherry could have different properties that i am not familiar with. The best way is to make a sort of quick dried mini-bow of the wood and see how far it can bend. That should give you a relative estimate of the woods strength and bowwood qualities.