The Least Useful Guide to Fukuoka

This is my first time to have seen this bean. My local greengrocer said that it was a disgrace not to try this. So I tried. Cut in round slices, the profile looks like lovely stars. Although she said it is a kind of string beans, I found its texture and taste more like courgette, like a washing-up sponge, boring and tasteless. If you know how to cook this, please let me know.