What is setsubun?

Setsubun is held one day before the first day of spring, which is February 3 or 4.
People open the doors of their houses and drive the demons, or bad luck, out of their homes by throwing soybeans and shouting "Out with demons! In with good luck!"
It was started originally as an imperial event on New Year's Eve for the purpose of getting rid of demons to welcome in a happy New Year.
Later it was incorporated with the indigenous custom of throwing soybeans at the time of planting rice seedlings, and it has thus evolved into its present form.