Lifespan: Unknown to Genki 2 (1571)
Other Names: Jōrinsai Zentō
Title: Governor of Noto
Lord: Daihōji Harutoki → Daihōji Yoshimasu → Daihōji Yoshiuji
Tosabayashi Zentō served as a bushō during the Sengoku period. He was a retainer of the Daihōji clan and served as the lord of Fujishima Castle in Tsuruoka in Dewa Province. Fujishima Castle was built on a plain with the Fujishima River serving as a natural barrier.
The Tosabayashi clan served as bettō, or stewards of Mount Haguro – the location of a sacred shrine known as the Idewa Shrine. The Tosabayashi possessed power on a par with the Daihōji clan but were decimated in a conflict with the Daihōji in 1477. During the Tenbun era (1532 to 1555), Zentō served the Daihōji again as the head among senior retainers.
In 1541, following the death of Daihōji Haruoki, the fifteenth head of the Daihōji clan, Zentō underwent the rites of tonsure and adopted the monk’s name of Jōrinsai Zentō. After the demise of Harutoki, Zentō backed Daihōji Yoshimasu. Around 1562, he sent a letter to Ise Sadataka, the secretary of the mandokoro, a central organ for managing the affairs of the bakufu, giving thanks for condolences from Ashikaga Yoshiteru, the thirteenth shōgun, upon the death of Zentō’s child. Later that same year, Sadataka was killed by Matsunaga Hisahide and the Ise clan fell into ruin. After losing the protection of Sadataka, an administrator for the clan named Ninagawa Chikayo inquired with Zentō about going to Dewa, and Zentō agreed.
In 1565, after Yoshiteru was murdered in a plot by Matsunaga Hisahide known as the Eiroku Incident, Chikayo finally gave-up his landholdings and fled to Dewa. He did not, however, reach the Shōnai area. While staying with the Takamatsu clan in the Sagae manor in the Murayama District, he died. This account indicates that Zentō had diplomatic relations with central figures in the Muromachi bakufu based on an alliance with the Sagae clan of the Murayama District through which ran a road connecting the Shōnai area and the interior portions of Dewa known as the rokujūrigoe road.
In 1568, after Honjō Shigenaga launched a rebellion against Uesugi Terutora (Uesugi Kenshin) known as the Revolt of Honjō Shigenaga, the Daihōji clan joined the Honjō so, after the suppression of the revolt, endeavored to forge a settlement with the Uesugi.
In the era of Yoshimasa’s successor, Daihōji Yoshiuji, Zentō continued to served as a deputy, but came into conflict with Yoshiuji over policies concerning the relationships with the Uesugi and the gōzoku, or wealthy families. As the relationship between Zentō and Yoshiuji deteriorated, through the mediation of Uesugi Kenshin in 1570, Zentō waited upon Yoshiuji at Oura Castle. Nevertheless, harboring suspicions fueled by rumors, he fled to Yokoyama Castle.
In 1571, he was killed in action during an attack by Yoshiuji.