"A knight has something he must protect." An era in which samurai piloted armed horses, traversed the universe, and spent their days engaged in battle. Fourteen years ago, in the Kingdom of Grieve, where the protagonist Chizuru lives, an internal conflict erupted between the "First Prince's faction" and the "Elders' faction" while the king was away. The conflict subsided with the king's return, but it was ultimately attributed to the First Prince's rebellion and ended in victory for the "Elders' faction." Chizuru's father, a knight who belonged to the "First Prince's faction," was forced to commit seppuku (ritual suicide) for his involvement in the rebellion . Chizuru joined the King's Royal Guard to uncover the truth about her father's death and seek revenge, but she gave up on her revenge and, disgusted by the reality of the Royal Guard and the world of knights, which was different from her ideals, she was considering leaving. Around this time, Chizuru was assigned to look after Eiks Rocca, a troublemaker who had joined the Royal Guard, and a new life within the Royal Guard began for her.