Can I eat Sophora japonica picked in rainy days?

You are talking about the most common Sophora japonica.

You can eat it, but it needs cleaning. When I was a child, I usually ate it raw. If you want to make cakes, you need to choose a lot. Actually, I think you'd better not eat it, because there will be bugs and it's unsanitary.

As for how to eat upstairs, you should consult carefully before making a decision, because there are really few people who can cook now. I'm in my twenties now, and there are no people who used to make Sophora japonica cakes for me.