Shun Sato

Overview

Shun Sato is the Lord of the Tower, known to the public as the Devil of the Tower and remembered as the third hero of the Demon War. Accounts of him divide sharply: some describe a kind, charismatic young man; others a devilishly cunning monster. He is the father of Ryuji Sato and Mimi Sato, served at the Tower by Zero.

The prologue records his intervention in the First Transgression, where he defeats Victor the Third’s invading army, and later in the Hikari Civil War, where he turns Satomi’s battle against Arata. Magnus punishes the latter breach, after which the Tower closes for a month. In His Return, Shun comes personally to the school, declares Ryuji guilty, defeats the students and their parents who oppose him, and takes his son back to the Tower.

The fugitive knight and the second transgression

Volume II reveals the human relationship behind Shun's most consequential breach of neutrality. When Yumi Raijin brings the dying Satomi Hikari to the Tower, Shun gives them sanctuary and binds Yumi to service as his price. Their hostility gradually becomes companionship. Yumi teaches his undisciplined swordsmanship a formal structure, plays the Lullaby of Haru beneath the Grand Tree, and becomes the person before whom he permits his loneliness to show.

Shun ultimately follows her into the Battle of a Thousand Shadows, openly intervening in human politics to save her and Satomi. Magnus answers that second transgression with imprisonment, starvation and the Unbreakable Oath. The oath requires Shun's first biological son to serve the Demon throne after reaching maturity unless the son defeats its strongest Royal Knight. Shun survives Magnus's punishment, but the black roses and thorns remain branded into his arm.

Husband, father and keeper of secrets

After returning to the Tower gravely wounded, Shun confesses the separate Reincarnation Curse to Yumi. She accepts both his uncertain lifespan and the danger surrounding him, and the two exchange lifelong vows. Sixteen years of family life follow. Shun and Yumi raise Ryuji Sato and Haruka Sato alongside Mimi Sato, but Shun's attempt to protect Ryuji through secrecy turns his parenting severe. From Ryuji's tenth year he trains the boy as a weapon without explaining the danger for which he is being prepared.

The concealment ends in catastrophe when Ryuji's inherited curse awakens and kills Yumi in the Tower courtyard. Shun recognizes his own corruption in his son, is driven by its voice to attack him, and must be restrained by Zero and Ryosuke. His grief later causes him to mistake Haruka for a monster and injure her. The incident exposes an old scar on his scalp and a memory of being beaten as a six-year-old child. Shun refuses Mimi's healing because the scar reminds him to be better than his own father.

The oath and the coming duel

Shun secretly orders Zero to watch the exiled Ryuji rather than drag him home. When the oath activates at the boy's maturity, Shun takes him from the School for Gifted Children and forces him back into training. He later explains that Magnus died a year after casting the oath but bound it to the throne. Its current beneficiary is Akiyama Magnus, Shun's former commander and trusted friend. If Ryuji loses the required duel, Akiyama has agreed to protect him and eventually release him from service.

Shun can tear finite fragments from his own shadow and merge them with remote shadows, creating sparse waypoints across both realms. A fragment joined to Mimi lets him summon her or travel directly to her. The technique explains his apparently limitless transit but carries a physical limit: every deployed fragment reduces the shadow remaining to him.

Before the duel, father and son finally apologize to one another. Ryuji asks for no more secrets; Shun promises despite still concealing a prophecy concerning a savior.