An Azusa Yumi (梓弓) is a sacred bow in Japan, as well as a Japanese (musical) bow made from the wood of the Japanese cherry birch Betula grossa tree (azusa, 梓). Playing an azusayumi forms part of some Shinto rituals. In Japanese poetry, the word azusayumi functions as a makurakotoba ("pillow word").
The story is told in Japanese mythology that a golden bird perched on the bow of Emperor Jimmu, the great grandson of the sun goddess Amaterasu, and the first human ruler of Japan. This was seen as an extremely good omen; Jimmu's bow developed the power to dispel evil by the mere plucking of its string. His bow was made of birch wood, in Japanese, "azusa".
Since that time, 59 Azusa-Yumi (29 vermilion and 30 black - vermilion signifying male energy and black female energy) have been enshrined at the Ise Grand Shrine, Japan's most important Shinto shrine and the main residence of Amaterasu. They serve to protect and purify the shrine's sacred inner chamber. These bows that are enshrined at Ise become Goshimpo-yumi (Great Treasures of the Gods). Every twenty years the inner chamber of the Shrine is renewed and new offerings are made — including the Goshimpo-yumi.
Nobility
It is also a long-standing tradition for the great lords and nobility to have a set of these sacred bows, either originals or replicas, in their homes (one vermilion; one black) and these are referred to as Gokaho-yumi or "Great Family Treasures". Azusa-Yumi are hand-carved from either catalpa or cherry wood, lacquered, and fitted with gold, silk cords and brocade.