Kasahara Masataka was a vassal of the Houjou Clan and master of Izu-Tokura Castle. His father was Matsuda Norihide, and he was adopted into the Kasahara Clan. He served Takeda Katsuyori for a while, but after the fall of the Takeda Clan returned to the Houjou. When his younger brother Matsuda Hideharu discovered him and his father passing information to the Toyotomi side during the Siege of Odawara, Masataka was forced to commit suicide.