A retainer of Uesugi Kagekatsu, Yokota Muneshun became lord of Nakayama Castle in 1598 when Kagekatsu was enfeoffed with 1.2 million koku in Aizu. On September 17, 1600, during the Battle of Dewa — fought in tandem with Sekigahara — he led some 4,000 troops from the Nakayama pass, together with Shinoi Yasunobu, to attack Kaminoyama Castle on the front line of the Ushu Highway. However, they were repelled by a counterattack from the castle's defender Satomi Minbu and pincered by Mogami reinforcements, suffering the death of the Uesugi commander Motomura Chikamori and being forced to retreat. Nakayama Castle was abandoned shortly after this battle.

A warrior entrusted by the Uesugi with a border castle, who personally led troops into battle on the front line of the Dewa campaign.

His attack on Kaminoyama Castle during the Battle of Dewa contributed to the failure of the Uesugi southward advance, after which the clan was drastically reduced to 300,000 koku at Yonezawa. Nakayama Castle later served as one of the five satellite castles of Yonezawa Domain during the Edo period.