"Oni-itaya" (Acer mono var. ambiguum) belongs to the Aceraceae (the Maple family). It is a tall deciduous tree that is native to Japan. This tree grows in wettish valleys and slopes, and can reach 15-20 m in height. The leaves are opposite, 10-25 cm long, and divided into 5-7 lobes palmately. They are dull and hairless above, and covered with fine hairs beneath. The yellowish green flowers bloom in April and May. The fruits are samara with right to acute angle opened wings.