Saitō Masayoshi served as a bushō during the Sengoku period.  He was the lord of Torimine Castle in the Kani District of Mino Province.

Masayoshi was born as the illegitimate son of Konoe Taneie, the kanpaku, or Chief Advisor to the Emperor.  At the age of thirteen, his father, Taneie, assigned a retainer named Seta Sakyō to him and sent him into the priesthood at the Yokogawa-Eshin Temple on Mount Hiei.  Sakyō originated from the village of Seta in the Kani District of Mino and Saitō Dōsan kept the older sister of Sakyō as a concubine.  Masayoshi had an interest in military affairs, so through the connection of Sakyō’s sister, he turned to Dōsan and was adopted.

Masayoshi used the name of Dainagon which was also used by Saitō Toshichika, the grandson of Saitō Myōchin.  Myōchin managed the Jizein sub-temple at the Zenne Temple so he was called Jizein-Myōchin.  Among the families affiliated with the Saitō clan, his lineage is referred to as the Jizein family.  Given the use of the same name by Masayoshi and Toshichika, there is a theory that Masayoshi inherited the Jizein family who were members of the Saitō clan.

In 1532, Masayoshi attended his coming-of-age ceremony at the age of sixteen.  He then followed Hineno Hironari and, with a contingent of 300 troops, participated in his first battle.  This was against Toki Yorizumi who stood in opposition to Dōsan.  Seeking a base of operations in eastern Mino, Dōsan proceeded to build a castle atop Mount Taka south of the village of Nakaido in the Kani District.  He then formed a garrison of 2,000 soldiers at the castle.

In 1537, with the cooperation of fourteen commanders in the area, Masayoshi constructed Torimine Castle but this is surmised to have been done with the backing of Dōsan.  In 1538, after Masayoshi entered the new castle, he called himself Dainagon.  This reflected a self-awareness as an heir of the Jizein family that began with Myōchin in the mid-Muromachi period.

Based on a comparison of the letter of commendation that Masayoshi provided to Imaeda Yahachi and the letters of commendation that Dōsan gave to numerous recipients, it does not appear that Masayoshi was of a lower status than Dōsan and under Toki Yoriaki, the military governor of Mino, Masayoshi is deemed to have been of equal status as Dōsan.

In the eighth month of 1539, Masayoshi ordered the painting of his life-size portrait dressed in armor.  This is kept to the present day at the Jōin Temple built by Masayoshi in Kaneyama in the city of Kani in Gifu Prefecture.  There is a tribute on the painting from Minshuku Keishun, an abbot at the Daien Temple in Iwamura in the Ena District.  This tribute is damaged so only a portion of the original remains.  The temple made copies of the text with augmentation of the missing portions.

In the second month of 1548, Masayoshi was invited to a banquet at the residence of a retainer named Kukuri Yorioki, the lord of Kukuri Castle, at which time he was murdered.  Masayoshi was thirty-three years old.  His remains were interred at the Jōon Temple.  Yorioki led a contingent of over 500 men to topple Torimine Castle and then had a member of his family, Toki Jūrōzaemon, serve as the guardian of the castle.  Given that Dōsan did not seek retribution and Yorioki did not move into Torimine Castle even though it was superior to Kukuri Castle, there is a view that Masayoshi’s accumulation of power did not sit well with Dōsan so Dōsan used Yorioki to eliminate him.

At the Jōon Temple, there is a gorintō, or five-part gravestone representing earth, water, fire, wind and heaven, which inscription states the date of death but it is badly worn and difficult to decipher.  He is presumed to have died in the second month of 1548 but may also have been around 1551.

Revenge killing of Kukuri Yorioki

In the first month of 1583, Yorioki, to attend a new year’s event including consultations regarding a deployment to Hida Province, joined Senchiyo (the younger brother of Mori Nagayoshi earlier tendered as a hostage) on a visit to Nagayoshi’s base at Kaneyama Castle.  They were received as guests until the evening.  While departing, at the Sugigadō entrance to Kaneyama Castle, Yorioki was assaulted and slayed by Kagiya Masanori to avenge the killing by Yorioki of his grandfather, Saitō Dainagon (Masayoshi).  Masanori was the son of Kagiya Masatsugu, the orphan of Masayoshi who was killed by Yorioki in 1548.