Kirk here with a little gif that is made up of a picture and a video that I took with my iPhone last night. On the left, a girl is holding a flower called a hotaru bukuro (蛍袋). In English, it can be called a “spotted bellflower” but the literal meaning of the Japanese name is “firefly bag.” What you see on the right is a firefly doing its thing inside that very “firefly bag.” Actually, I took the photo on the left by mistake; I forgot to turn off the flash. But, now I think it was a rather happy accident, so to speak, because it gives you an idea of what is actually happening.
The flower and the firefly were found in the same spot, just outside the home of a friend who lives in the Mifune area. Firefly season started earlier in May and extends into the first part of June.
Information in English about the plant: https://hayakawajunpei.tumblr.com/post/96059350936/hotaru-bukuro-campanula-punctata-common-english