Since west represented autumn in gogyo-setsu (the theory of five elements) and Mt. Tatsuta to the west of Heijo-kyo (the ancient capital of Japan in current Nara) was famous for beautiful colored autumnal leaves, the beauty of the mountain led people to believe that a goddess of autumn lived there.
五行説では西は秋に通じ、また平城京の西に位置する竜田山は古くから紅葉の名所として有名だったため、その山の美しさから秋の女神が住むと信じられてきた。