Okay, kiddo, let me explain. You know how in some places there are really tall buildings that have lots of floors, right? Well, in Japan, there are special buildings called pagodas. They are tall and have many floors, too, but they look different because they are shaped like a tower with a pointed top.
Now, a long time ago, in a place called Yanaka in Japan, there was a pagoda that was very old and very special. People used to go and visit it because it was beautiful and had been there for many years.
Unfortunately, one day some bad people decided to do a very, very bad thing. They set fire to the pagoda on purpose, meaning they made it burn down. The fire was so big that the pagoda was completely destroyed, and it was a very sad thing for the people who lived in Yanaka.
But that's not all, kiddo. Two people decided to do something even worse. They went to the place where the pagoda had once stood, and they set themselves on fire as well. This is called suicide, and it is a terrible thing to do.
So, in short, Yanaka Five-Storied Pagoda Double-Suicide Arson Case refers to the sad event where someone set fire to a special pagoda in Japan, and then two other people decided to take their own lives near the same place. It was a very, very sad thing that happened.