Nagakiyo who appears as 'Kojiro Nagakiyo KAGAMI' in "Heike Monogatari" (The Tale of the Heike), called himself Ogasawara clan after he inherited the territory of Tomitsu in Ogasawara of Kai Province.
長清は『平家物語』に「加賀美小次郎長清」の名で登場しており、遠光の所領の甲斐国小笠原を相続して小笠原氏を称した。