Mizuho Plain

View of the Mizuho Plain and the Sunomata River from Mount Miyoshi (三好)

The Mizuho Plain is a large plain in Yamatai that encompasses much of Mizuho Province, as well as the eastern part of Yamashiro Province, east of the Hiroka River. It is an alluvial plain created by the Three Rivers of Mizuho (Sunomata, Ibi, and Kiso Rivers) and has very fertile soil. It is bordered on the west by the Sayashi Mountains and on the east by the Aki Strait.

The Mizuho Plain is considered one of the most important agricultural areas in Yamatai, and is a major breadbasket for the country. Historically, the feudal clans that controlled the Mizuho Plain were often amongst the richest and more powerful clans due to their control of the food supply. Numerous wars were fought over the Mizuho Plain during the feudal era, with the most famous being the Mizuho War in the 12th century, when fighting over the Mizuho Plain developed into a major nationwide civil war due to complex clan alliances. The last clan to be in control of the Mizuho Plain by the Aozora Revolution was the Ikaruga Clan, which controlled the area now occupied by Mizuho Province. The Shinohara Clan controlled the southern part of the Plain, in the area now part of Yamashiro Province.

Today, the numerous farms in the Mizuho Plain still account for the largest percentage of national agricultural output.