Asari Masatane served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of the Kai-Takeda clan. Masatane received one of the characters from the name of Takeda Katsuyori and had the separate name of Katsuari.
Masatane was born as the eldest son and designated heir of Asari Nobutane. In 1569, at the Battle of Mimasetōge, his father, Nobutane, was killed so he succeeded him as a samurai general but only 60 mounted soldiers (amounting to one-half of those serving his deceased father) followed Masatane. Later, in 1575, after Tsuchiya Masatsugu (a hereditary chief retainer of the Kai-Takeda) died at the Battle of Nagashino, Masatane inherited 60 more mounted soldiers comprising a battalion of 120 soldiers in total.
After the demise of the Takeda clan in the third month of 1582, Masatane served the Tokugawa clan and was assigned to Honda Tadakatsu. Honda Shigetsugu, a retainer of the Tokugawa, in reference to Masatane during this period, noted: “It is a pity that Asari-dono who is respected within the Takeda family and under the command of Honda Tadakatsu always appears to flatter those from the Matsushita and Sakisaka by being in a lower seat.”