According to the expository writing of "Hyakki Tsurezure Bukuro," the 'Furu-utsubo' (an old quiver) used to belong to Yoshiaki MIURA who shot yakan (Buddhist legendary animals, which initially referred to jackals in India and later foxes in Japan) in Nasunogahara fields.
『百器徒然袋』の解説文によれば、この「古空穂」は元は那須野ヶ原で野干を射たという三浦義明の空穂だったとある。