I don't know enough about Japanese cooking to comment extensively on that, but I do know that there is an ingredient called sanshō that looks similar to green S

I don't know enough about Japanese cooking to comment extensively on that, but I do know that there is an ingredient called sanshō that looks similar to green Sichuan peppers. That is not the ingredient I am talking about. From my observations living in China, shopping at wet markets and eating in restaurants, green Sichuan pepper is quite commonly used. Both red and green variants are sold in dry format, but the red ones are the ones you will find more often pre-packaged in supermarkets. They do both work to create a numbing sensation, but in my opinion, the green ones get you more bang for your buck.