|Occupation||First Prince of New Yogo|
|Novel||Moribito: Guardian of the Spirit (mentioned)|
|English||Johnny Yong Bosch|
In the first novel, Sagum is mentioned as an aloof individual who appears to disdain Second Prince in Chagum's recollections of his older brother and they do not have a close relationship. Sagum falls ill late in the novel, which forces Shuga and the Hunters to increase their efforts to bring Chagum back to the palace when it becomes apparent that if Sagum should die, Chagum will be the sole heir to the throne. Despite the Master Star Reader's efforts, Sagum dies. The third novel of the series suggests that Chagum and Sagum may have actually had a closer relationship than previously implied.
In the anime, Sagum is depicted as a considerably kinder young man with a reserved nature. Though he is responsible and studious, he feels that Chagum would be more suitable as a ruler because he is compassionate and empathetic. He and Chagum have a close relationship, spending time together in the palace gardens when they could get away from their studies. Sagum cares for his brother deeply, and takes measures to protect Chagum's personal belongings when they are taken to be burned after Chagum is presumed dead. Upon realizing how much Sagum cared for his brother, Shuga places more effort in his investigations to find Chagum and hopes to bring the Second Prince back to the palace.
However, the burden of his responsibilities of crown prince takes its toll on Sagum's health and he dies of overwork before being able to see Chagum again. Before dying, he releases a pet Nahji bird in his possession, after which his tutor Gakai finds the prince is no longer alive. Shuga blames his own lack of ability to find Chagum before Sagum's death and Chagum is distraught upon discovering that Sagum has died, which almost jeopardizes Balsa's efforts to learn how to save Chagum and the Water Spirit.