Emperor Yang of Sui
The exact origin of the "Hinomaru" is unknown, but the rising sun had some symbolic meaning since the early 7th century (the Japanese archipelago is east of the Asian mainland, and is thus where the sun "rises"). In 607, an official correspondence that began with "from the Emperor of the rising sun" was sent to Chinese Emperor Yang of Sui. Japan is often referred to as "the land of the rising sun".