Black Sperm

Small and strange to look at, Black Sperm barely reaches the height of the fighters around him. His frame is inked entirely black, broken only by a pale face that carries a pair of dark eyes, while a slim tail-shaped stalk juts from the crown of his head. Artists tend to render him with far simpler linework than the rest of the cast, a nod to the plainer look of ONE's original webcomic.

Pride and deep insecurity war inside Black Sperm. He trusts his own strength enough to have once squared off against Monster King Orochi, yet any hint that others sneer at his looks or manner throws him into a rage, and the loss of his clones provokes the same fury. Facing a genuinely stronger foe, he sets ego aside and cooperates, which is what bound him to the Monster Association. When the tide runs his way he turns cruel and gloating, as he did toward Genos, though he keeps a wary guard up against threats like King.

The creation of Platinum Sperm leaves him torn between grief and elation, mourning the trillions of cells sacrificed while celebrating the arrival of what he calls his true self. Human lives mean little to him, and he showed no qualms about killing the captive boy Tareo. His crushing defeat by Garou, and the sight of Saitama then flattening the Hero Hunter, humbles him; afterward he quietly rebuilds his cell reserves and chooses to shelter beside whoever happens to be strongest.

Everything about Black Sperm's power flows from his cell count: the more copies he holds, the stronger he grows, and a fully stocked version can bury Genos in the ground or physically restrain the elite Sweet Mask. A lone clone hits hard enough to bloody Atomic Samurai, and Homeless Emperor rated a single clone as enough to finish an A-Class hero, since the monster's dividing body was a near-perfect counter to the swordsman's slashing style. He moves and reacts with surprising quickness for his size, digs his way back up after being buried, and can reshape his body at will, sprouting extra heads or limbs and stretching them outward.

His defining trait is Replication. Rather than die from a lethal cut, he divides into fresh duplicates so long as reserves remain, though blunt or acidic blows that fail to slice him simply make his clones burst. Damage only lowers his running total, and severed pieces knit back into more of himself while he has cells to spare, which he replenishes by eating protein. When he commits, he fuses cells irreversibly through Coalescence, and the larger the merge the stronger and more arrogant the result: a mass of roughly 43 to 55 trillion cells becomes the golden, muscular Golden Sperm, while an even greater fusion yields the sleeker, shinier Platinum Sperm. Stripped of his stock after the association's collapse, the final surviving clone grows so feeble that even a puppy can beat it.