Ancient Japan traded things they were good at producing .... pottery, armor and weapons, cloth, carvings, daggers, jade, combs made of shells, and other household items, Clay figures known as dogū,
(Some of the oldest surviving examples of pottery in the world may be found in Japan)
Some casting of bronze and iron began in Japan by about 100 BCE so everything imaginable from art to weapons.
Being an island with limited natural resources the Japanese became adept at arts and crafts and textiles, sword and armor making ..... things they could trade for natural resources like wood, rice, red beans, soybeans and millet .
They traded with the Gojoseon.
They Gojoseon were the descendants of migrating Altaic tribes that settled in Manchuria, far eastern China north of the Yangtze River, and the Korean Peninsula.
There were also the Jin and the Samhan.
After the fall of Gojoseon, Buyeo arose in today's North Korea and southern Manchuria, from about the 2nd century BC to 494. Its remnants were absorbed by Goguryeo in 494
On the Southern coast (their Northern coasts) they traded with the Baekje, Silla, and Gaya.
Silla artifacts, including unique gold metalwork, show influence from the (white) northern nomadic steppes, with a lot less Chinese influence than are shown by Goguryeo and Baekje. Silla expanded rapidly by occupying the Han River basin and uniting the city states.
They also traded with the Wei and Liu Song to their west on the Northwestern coast of what is modern day China.
Do NOT make the mistake in thinking that these people were the SAME people they are today.
This area once had been a HUGE traffic area of more European looking people that were headed across the Bering Strait into modern day Canada.
Genetics show us that migration later by island hopping by boat was a lot more recent than previously thought.
Earliest photos of southern Silla show them with much darker skin tone like Polynesians or even American Eskimos.
All in all, Japan did a huge water trade with many different nations and since they were short on natural resources they expanded their knowledge in crafts, textiles, metal working and ship making
Mainly China, but also Korea. They traded pretty much everything, because Japan being an island had limited resources. Some of the more popular items were jade, metal, food etc...