Japan during the Cataclysm.
The "Homeland" of the Samurai, as they call, was the original land of the Samurai, an island far to the East, before their arrival in Heathmoor and settlement of The Myre. After the Cataclysm, it sunk into the ocean, never to be seen again.
It can be inferred that the homeland in question is what is known as Japan in the real world.
Overview[]
Long ago, the Homeland was an island nation often talked about and romanticized by the Samurai of the Dawn Empire. After The Great Cataclysm, the population feared that their island nation was no longer safe to stay. In response, the Emperor created a massive fleet of ships and loaded up as many people, animals, plants, and equipment as they could. They sent out that fleet of ships to search for safe haven for their civilization. Their Emperor would stay behind to ensure more people would be safe.
After many nomadic travels, and gaining knowledge from many different peoples, their search brought them to The Myre, an inhospitable swamp land that was once nothing but ocean. However, the situation was far worse than they expected. While the refugee fleet was out, Japan and all its inhabitants sunk into the ocean. When the Samurai sent ships back to send word of safe harbor, it was too late. Their home had been swallowed up by the ocean. Worse, their Emperor was one of the casualties. Since then, the Samurai have done efforts to terraform the swampland, making it somewhat like their homeland; including planting cherry trees along with other native plants in places where they would not normally grow.