Drum of Heaven.

Heian era Japan. A gentleman discovers an abandoned baby and raises the boy as his adopted son, naming him Nijihito after the rainbow in the sky at the time he was found. The only clue to the boy’s origin is a special drum found with him. Nijihito proves to be a drumming prodigy, outshining his best friend Tatsuru. Although young Ibuki is secretly in love with Nijihito, he falls in love with a mysterious woman he sees playing the flute outside one night.