Morikiyo Ideura, a retainer of the Sanada clan, originated from the Hanishina region of Shinano Province (present-day Sakaki). He demonstrated exceptional loyalty following the Honno-ji Incident by aiding his betrayed vassal lord, Mori Nagayoshi, during the retreat from Shinano Province, standing as Nagayoshi's sole supporter. This act earned him Nagayoshi's wakizashi as a token of profound gratitude. In early 1583, under the command of Sanada Masayuki and Nobuyuki, he commanded the Agatsuma Shinobi Clan. His leadership proved instrumental in successful military campaigns, including the siege of Oshi Castle. Later, he assumed the position of the first ninja head for the Matsushiro Domain, executing duties typically reserved for samurai.