Pine needle disaster

In the Kingdom of the Rising Sun, all residents are rheumatoid who eat pine needles and pine needles alone.  about one hundred years ago, there was a droit, which led to a dry summer, and near the end of the dry summer, a forest fire broke out and devastated their pine tree pastures, taking most of their crop and fields which had been growing for hundreds of years.
Food became very scarce for years to come as new fields were planted and raised.  A border between the Kingdom of the Rising Sun and Kingdom of the Elements became difficult to maintain as starving rheumatoids crossed to keep their families fed.  The kingdom of the Elements is home to a lush pine forest left untouched by the fires. Their people do not eat pine needles.  The Kingdom the Elements rescued the Kingdom the Rising Sun from starvation.
A trade route was established and borders were opened between the two countries.  This alliance remains to this day.  The trade route started as a dirt path in which carts carried billions of pine needles to the starving population of the Rising Sun.  Now, it is a large ramp that runs once every day using Thunder Carts. Pine needles are no longer traded, as The Kingdom of the Rising Sun has well-established fields now, with amazing irrigation thanks to the practices the kingdom of the Elements taught them.
Metals, animals and grains are traded, jewelry, and clothing.  This has lead to two countries having styles that reflect one another's history.  Fashion today in both countries usually line up and share many elements.  A hilarious trend that now has taken hold in the kingdom of the Elements is wearing a top with a triangle cut out in the upper back.  This comes from the winged people of the kingdom of the Rising Sun.  It is funny that the Kingdom of the Elements now wears this, as they have no wings, it is simply fashionable there after a hundred years of trading and cultural integration.