Cusack

Name: Cusack

Gender: Male

Race: Demon (First Demon half)

Age: 6000 years old

Height: 195 cm

Weight: 100 kg

Blood Type: A

Birthday: November 1

Power Level: 168,000 (with power released)

Alias: Slumbering Reaper

Occupation/Role: Zeldris’s swordmaster and butler

Voice Actor (Japanese): Jouji Nakata

Cusack is one of the highest-ranking demons and is described, alongside Chandler, as one of the oldest members of the Demon Clan.

Despite having his original power sealed, he is considered one of the strongest demons after the Demon King himself.

He fights as a dual-wielding swordsman and is a master of swordsmanship.

He trained Zeldris personally, passing on his techniques and combat style.

Cusack is feared for his ability to instantly dominate a target’s mind and take full control over their life and death.

Because his victims fall as if drifting into sleep, he earned the ominous nickname “Slumbering Reaper.”

Cusack is Zeldris’s combat mentor and shows an intense, almost doting attachment to his disciple.

He takes pride not just in Zeldris’s strength but also in serving as his butler, though the tea he brews is notably terrible.

He has absolute confidence in his appearance, especially his two long, straight mustache-like whiskers.

He even claims that his facial hair is the finest in the Demon Realm.

Normally, Cusack is calm, collected, and calculating, often giving the impression that he is scheming something in the background.

However, this composure shatters when his prized facial hair is damaged or when Zeldris’s life is in danger.

In those moments, he shows a temperament very similar to Chandler’s, abandoning all rationality and restraint.

Although there are many hints that he is plotting something larger, much of his inner thinking remains unexplored and underdeveloped in the story.

Cusack’s power level reaches 168,000 when he releases his sealed strength.

Even with his original power restricted, he stands at the pinnacle of the Demon Clan below the Demon King.

He is a highly skilled dual-wielding swordsman.

His swordsmanship is so refined that Zeldris, one of the most formidable demons, learned his techniques directly from Cusack.

When he gets serious, Cusack transforms into a far more demonic and ominous form.

Like Chandler, in this state wings sprout from his back and his appearance becomes more monstrous, reflecting his true demonic nature.

He can dominate a target’s mind at a glance, removing any control they have over their actions.

This mental control can reach targets even at some distance, making him extremely dangerous in both direct and indirect confrontations.

Magic Name: Resonant

Resonant allows Cusack to send his magical power into a target through eye contact.

Once affected, the victim’s mind is taken over, and Cusack can rob them of any control over their own life and death.

One basic application is forced mirroring: the affected target is compelled to perform the same motions as Cusack himself.

This turns his own movements into a direct and unavoidable command over the opponent’s body.

In the story, he uses this power on Arthur Pendragon, whom Merlin has brought back.

By synchronizing Arthur’s movements with his own, Cusack forces Arthur to stab himself with Excalibur, resulting in Arthur’s apparent death.

Resonant can also be used to intrude into a target’s inner world or mental space.

However, because the ability is shown only a few times, many finer details and limits of Resonant remain unknown.

Cusack serves Zeldris as both master and attendant, acting like a strict yet deeply attached mentor.

He supports Zeldris’s ambitions and sees in him the future of the Demon Clan.

After he and Chandler return to their original forms and then split again, Cusack becomes more proactive and ruthless.

He formulates a plan to make Zeldris the new Demon King.

Seeing Chandler as an obstacle to this goal, Cusack goes as far as killing Chandler.

He then has Zeldris absorb Commandments, pushing his disciple toward godlike power.

However, this plan backfires in the worst possible way.

The power he forces onto Zeldris allows the Demon King to use Zeldris’s body as a new vessel.

Cusack’s actions, meant to protect and empower his beloved disciple, instead doom Zeldris to become the Demon King’s host.

Before Cusack can fully understand the consequences of what he has done, he is erased by the Demon King.

Cusack’s true identity is that of one half of the First Demon created by the Demon King.

Long ago, the Demon King split the original First Demon into two separate bodies and minds.

These two resulting beings are Cusack and Chandler.

Together, they represent the divided form of the Demon King’s primordial demon creation, sharing a deep, intertwined origin even as they clash in their final actions.