Ok kiddo, have you ever seen those funny drawings where people are making silly faces and blowing raspberries? That’s kind of what he-gassen is but in old Japan!
He-gassen is a Japanese word that means "Fart Battle Picture." It was a type of funny drawing that became popular during the Edo period in Japan, which is a long time ago.
The drawings usually show a bunch of people - either men, women, or even animals - all making faces while passing gas. Sometimes they'd be doing it at each other, as a kind of fart battle - hence the name.
Now, this may seem silly and childish, but these drawings had a deeper meaning. They were a way to make fun of people in power, like samurai warriors or government officials. It was also a way for regular people to show their frustrations with the ruling class in a way that was amusing and not too dangerous.
So there you have it, he-gassen is a type of funny drawing from long ago in Japan that showed people making faces and passing gas. But it was more than just a silly picture, it was a way for people to express their opinions and make fun of those in power.