The Yamato tribes were the first to realize that there was a vast ocean beyond the Iron Belt. When they mapped the island of Jamphel Yeshe in 143 AID by circumnavigating it, they called it Kujirajima, 'Whale Island', due to its likeness to a whale's head. People still sometimes use that name to illustrate it as a place that swallows people whole and then slowly and painfully digests them.
The Five Sages traveled the Great Land for many centuries until valiant explorers crossed the Iron Belt and found there a great ocean to the south. They left their peoples and joined in silent meditation on the First Island, and they built a monastery where they taught those who came to hear their wisdom, calling it Jamphel Yeshe.