This event is often done at nursery schools, primary schools or in the families who have little kids. Usually teachers or the father put the oni mask on and pretend that they are the ogres. Then kids chase him and throw the beans at him saying "Oni wa soto! (鬼は外 / ogres out!)". After getting rid of bad spirits, then throw the beans from the outside to the inside saying "Fuku wa uchi! (福は内 / good luck inside!)".
The literal meaning of Setsubun is to divide setsu = seasons; Risshun (立春), Rikka (立夏), Risshuu (立秋) and Rittou (立冬) and ancient Japanese people considered that apart from those days, the season officially changed. Also in lunar calendar, spring was the New Year, means Risshun was the New Year´s Eve.
In Nara period (奈良時代), to start a new year clean and fresh, people did special ceremonies, especially inside the Court. Those ceremonies were called Tsuina (追儺) that was done in order to get rid of demons and plagues. And throwing beans (Mame-maki / 豆まき) was one of Tsuina.
Tsuina was introduced from China during the Emperor Monmu (文武天皇, 697-707), at the beginning it was an annual event in the Court then later extended among the temples and the shrines in Japan.
One of the Japanese ukiyoe masters in Edo period, Hokusai Katsushika (葛飾北斎 / 1760-1849) left a work piece of Mame-maki.
We can still see the traditional Setsubun event in Heian Jingu (平安神宮) in Kyoto.
This is a video from 2011.
Traditionally, only Toshi-otoko (年男) who were born in a year with the same animal year as the current year (this year is dragon) or the head of the house. The rest of the family members eat as many beans as their age. When I was little, I always wanted to age quicker so that I could have more beans. Actually the day after, there was still a bag of beans and I could eat as much as I liked.
There are several theories but they have something in common.
Soybeans is one of five common cereals in Japan. It was the second more important cereal after rice and it was often used for ceremonies as people believed that there was a spirit in soybeans.
Also as the sound of beans in Japanese (Mame / 豆) can be heard similar to "the eyes of demons" (Ma no me / 魔の目) or "destroy the demons (Mametsu / 魔滅), soybeans started to be used.
One important thing is, the beans used for Mamemaki is always roasted. Why? One, because roast in Japanese, iru (炒る) has the same sound as "shoot (iru / 射る)". Second, this happens often, always some beans get lost and if the beans are fresh, they start to shoot. This is very unlucky. Imagine, Mame=demon´s eyes start blooming, that can be good, can´t it? So to kill the bad spirit, beans have to be roasted well.
At many houses´ door, you may see a head of sardine stuck into a holly branch. This comes from the myth that Oni doesn´t like smelly fish and spiky leaves.
My family never had this, but I guess that was just because my father didn´t like fish and it´d be a problem he had to enter the house passing by this smelly stuff all day.
Now, in some regions, on setsubun people eat futomaki (太巻き), not a slice of it but a whole roll per person. It was when I was in a high school, a classmate whose parents were from Osaka and once she told me that they would eat whole futomaki. Then she strangely added that they all faced to the same direction and were not allowed to talk during they ate it.
This is called Ehou-maki (恵方巻き), Ehou means a good direction and each year, you need to face to the certain direction. It was north-northwest this year.
It has be a fat roll sushi because it tends to have seven ingredients after the Seven fortune Gods and as it´s rolled, you rolled in all the luck. And you have to eat whole roll because if you cut it, you are cutting a good luck.
Anyway, this custom is now getting into Kanto area (eastern part of Japan) and you see many supermarkets and Konbini are selling futomaki on the 3rd of February.
I personally think that this is a plot of sushi shops and as I was told that while you eat the futomaki, you are not supposed to talk because you are praying for the year, I don´t think I would be able to think too much as I would be so concentrated not to choke myself with this chunk of sticky rice.
This is how we spend the beginning of "spring". It´s too cold to believe that the spring is just around the corner. Wrap up well everyone, stay warm.