The Reaper

His looks work against the dread his name inspires. The face he presents to the world is warm and disarming, and in his florist cover he sports silver hair, amber eyes, and a signature cap, switching to all-black attire when killing. Beneath that mask lies horror, since he sliced his own skin away, leaving a bare skull crowned only by hair. He can also weaponize his killing intent to cloak himself in a dark, ghostly silhouette.

The final arc reshapes him completely. Injected by Shiro with an intensified strain of the Antimatter Tentacles, he swells into an enormous dark creature echoing Korosensei's earliest tentacle shape. Writhing black appendages take the place of his arms, head, and legs, giving him the form of a colossal monster in shadowed tones.

Ranked among the deadliest assassins alive, he is calculating and merciless, ready to embrace any method however vile to reach his objective. Human life means nothing to him. He regards the students as mere hindrances and had no hesitation about drowning them to reach Korosensei, later skewering Kaede Kayano the instant she got in his way after his augmentation. Like the master he betrayed, he wears a gentle, trustworthy smile that leaves victims unable to sense danger; even Nagisa felt no unease around him, a blankness that unnerved Karma.

His coldness grew from a wound. He had once idolized his teacher and strained endlessly for a word of approval. Discovering that he was regarded as nothing but a useful instrument shattered that devotion and turned him against the man. Yet the craving for recognition never fully died, surfacing again as tentacles reshaped his body and lingering in his dying breath.

He was born into great wealth, and his path began the night his father was slain by the first Reaper. Watching the killing unfold through a window, he was enthralled rather than horrified, praising the elegance of the act and resolving to apprentice himself to the assassin responsible. His teacher, however, brushed aside his pleas for praise, and the realization that he was only a tool to be honed drove him to betray the man mid-mission, seize the Reaper name, and let his master be captured. To bury any hint of a successor, he copied his teacher's methods and kept his contacts. The grim upbringing he would later feed to Karasuma was invented; that history truly belonged to the original.

He first enters the plot as a rumor, named by Lovro when Nagisa asks after the world's greatest killer, having already left both Lovro and Red Eye near death. Posing as a florist, he sold Class 3-E bugged flowers to spy on Irina, then seized the window left open by Korosensei's trip to Brazil. Showing the students a photo of a captive Irina and threatening to return her in pieces, he lured them to a hideout and caged them with anti-sensei material, meaning to trap their teacher too. When the class blasted the wall open, he dropped his disguise and cut down the attack squad in under a minute, even overpowering Nagisa's stunning technique with a stronger version of his own.

His scheme unraveled against Karasuma, the one man able to rival his speed and close combat. As the two fought, the Reaper's mask tore away to reveal his skinless face, and his hidden weapon, the Invisible Scythe, fired a tiny round meant for Karasuma's heart, only for Korosensei's tentacle to catch the bullet. Beaten unconscious and taken into custody, he was found by Shiro, who revealed that Korosensei had been his old master and offered a shared vengeance. Rebuilt with antimatter tentacles into a monster faster than Korosensei himself, he broke through the anti-tentacle barrier for a final assault, briefly overwhelming his former teacher before being knifed and driven into the barrier. In his last words he confessed he had only ever wanted to be acknowledged and to become like the man before him, a wish Korosensei returned with sorrow as the Reaper's body crumbled away.