Saiunkoku is a world divided into eight provinces, each named after a different colour. The new emperor, Shi Ryuuki, is known for his indifference to court matters and for openly expressing affection for men. Shuurei, born into the influential Kou family but struggling to make ends meet, accepts an invitation to become the emperor’s concubine in hopes of turning him into a good ruler. The enigmatic Seiran, a young man adopted by her father, accompanies her as Ryuuki’s bodyguard. By entering the imperial palace, Shuurei rekindles her dream of serving as a court official, and, together with the many companions she meets along the way, she moves forward bravely while trying to fend off the emperor’s advances.