A nightingale, a rare species that can become a man or a woman at the request of its master. A 17-year-old Nightingale Milha is attacked by thieves when he heads to the royal capital to return the favor to the village by becoming a swordsman. The person he promised to cry all night long as a "bird" if he saves his life is Prince Rashik, who has been promised the throne in the Kingdom of Irksha...!?