A very long time ago, something huge happened! A big volcano erupted under the sea near Japan. It was one of the biggest eruptions ever! Hot rocks and ash flew everywhere. The ash covered the land for a long time.
People lived in Japan at that time. They hunted animals and gathered food from nature. The ash hurt the forests and rivers. So the people had to find new places. Many of them moved to the coast.
Near the sea, life came back fast. Fish and sea animals recovered quickly. The people started to eat food from the sea. Some groups even grew bigger than before! Scientists were very surprised by this discovery.
