Japanese hardcore is a type of music that is very loud and fast. It is often called "japcore" for short! Like all music, it has a lot of different sounds and styles, but it's generally known for intense, aggressive vocals, heavy electric guitars, and crazy drumming.
It's a bit like yelling really loudly with your friends and hitting things really hard. Sometimes the singers will just scream and shout instead of actually singing, and the guitar players will use distortion to make their guitars sound extra crunchy and angry. And the drummers will hit their drums super quickly, often going faster and faster until they're practically just a blur!
People who really like japcore like how powerful and intense it is. They might even start mosh pits at concerts, where they bump into each other and jump around in a big group.
So basically, Japanese hardcore is a kind of music that is very energetic and raw. It's not everyone's cup of tea, but for the people who love it, it's like a super exciting and intense way to express themselves!