Trim the roots of shimeji mushrooms and separate them by hand. Trim the roots of eringi mushrooms, cut them in half horizontally, then slice thinly lengthwise. Trim the roots of enoki mushrooms and separate them by hand.

Mix the marinade ingredients (sugar, salt, vinegar, pepper, olive oil) in a bowl.

Boil water in a pot, add the prepared mushrooms, and cook for 1 minute. Drain the water.