I've been to Japan nearly 40 times, and became well-acquainted with its cuisine. Shishito (accent on the first syllable) is a small pepper with a unique flavor. It is nominally not hot, but once in a while you might encounter one that is. A related pepper is the Padron, which comes from Spain. In truth, Columbus brought the padron to Iberia from the New World, and many years later, the Portuguese brought the padron to Japan, where is was hybridized into a different shape. Thus, the shishito and the padron have a similar flavor profile.
Shishito are used as everything from a garnish to a street food in Japan, whereas padron are most commonly encountered in tapas. You will find the shishito in Asian markets, particularly those that cater to Japanese or Korean ethnicities. You may find padron in Latin markets or stores catering to Spanish cuisine. Trust me they are worth seeking out.The European way of preparing padron is to grill or pan-fry them them in EVOO until slightly charred, then serve them sprinkled with a fancy salt and drizzled with lemon juice.
The European way of preparing padron is to grill or pan-fry them them in extra virgin olive oil until slightly charred, then serve them sprinkled with a fancy salt and drizzled with lemon juice.
In Japan, shishito are often skewered and grilled, turning and brushing every 30 seconds with a mixture of soy sauce and sake until slightly charred and blistered. They are also fried tempura-style, served with a sprinkling of togarashi, a mixture of several spices that you can buy in an Asian market or order online.