The following section contains Webcomic spoilers. You have been warned, manga-only readers.
As Golden Sperm he's considered to be the most powerful member of the Monster Association right after the Monster King Orochi himself.
After the Monster Associations downfall, he became Saitama's pet alongside Overgrown Rover and is currently under the watch of Forte, Chain'n'toad and Butterfly DX. He's also one of the few people who are fully aware of Saitama's strength, due to him being a witness of his fight against Garou.
Black Sperm is an odd-looking humanoid monster of diminutive stature. He has a fully black body and a pale white face with glowing eyes, and a tail-like extension protruding from the top of his head. Like Saitama and sometimes Tatsumaki, in the manga and anime he is often portrayed in a more simplistic style than the rest of the cast, reminiscent of ONE's original webcomic.
Black Sperm seems to be very confident in his abilities shown in his willingness to take on Orochi and dislikes when other people "look down on him since he is a sperm looking creature". However, he is also willing to work with others in order to take on a stronger opponent, shown by his cooperation with the Monster Assocation.
The following section contains Webcomic spoilers. You have been warned, manga-only readers.
Like other monsters, Black Sperm appears to care little for the lives of humans as he was about to kill the child kidnapped by the Monster Association without remorse. Likely due to his nature, he is accustomed to teamwork and is often the one to suggest teaming up with the other executives to take on strong enemies such as Tatsumaki. As more sperm cells merge together, the newly formed cell copies become more and more arrogant. When Golden Sperm is formed, the newly formed sperm copy becomes extremely arrogant, not even caring about his other sperm copies and telling them to simply merge with him due to his superior power.
The following section contains Webcomic spoilers. You have been warned, manga-only readers.
Sweet Mask himself says that even if all of the S-Class heroes fought Golden Sperm, it would still be a very difficult task to defeat him. Along with this, he was the only one besides Saitama who was able to fight against evolved Garou on equal footing, even if it was only for a few moments. It is possible that, in the manga, Golden Sperm is the most powerful member of the Monster Association. Murata does not know who is stronger between Golden Sperm and Orochi in terms of raw strength, although Orochi is a more advanced combatant.[2]
Immense Speed and Reflexes: Black Sperm is quick enough to dodge Atomic Samurai's slashes.
The following section contains Webcomic spoilers. You have been warned, manga-only readers.
As an individual Black Sperm, he was able to keep up with Genos's immense speed effortlessly.
Immense Strength: Contrary to his appearance, Black Sperm has great strength and was able to badly damage Atomic Samurai in one hit.
The following section contains Webcomic spoilers. You have been warned, manga-only readers.
He was also capable of lifting a huge boulder thrown at him by Sweet Mask with ease, as well as tear off one of Genos's arms.
Immense Durability: As a Dragon-level monster, Black Sperm possesses enormous durability. As an individual Black Sperm, he was able to easily withstand all of Atomic Samurai's attacks. Though he is still vulnerable to the more powerful Focused Atomic Slash.
Shapeshifting: Black Sperm is able to increase in size and manipulate his body shape in any way he chooses. He is capable of growing additional limbs; typically growing extra legs to support the weight of his larger forms.
Replication: Instead of being killed, whenever he is dealt a fatal blow that would typically result in death, Black Sperm will split into even more copies of himself if he still has enough cell stock. He can also split himself at will. However, this ability does have a weakness: if enough powerful blows are dealt fast enough to a Black Sperm copy, that copy will not be able to replicate in time and will die with all of its cell stock inside.
The following section contains Webcomic spoilers. You have been warned, manga-only readers.
Additionally, if the Black Sperm cells decide to merge into one being, they lose the ability to separate upon injury, making them much more vulnerable.
Hand-to-Hand Combatant: Black Sperm mainly relies on his brute strength and his skill in close-quarters combat during battles.
Kamikaze Attack: Black Sperm sacrifices a number of his cells to attack a target. This has been mainly used as a distraction.
The following section contains Webcomic spoilers. You have been warned, manga-only readers.
Coalescence (合体, Gattai): Black Sperm permanently combines his cells to form a more powerful version of himself. The more cells that he combines, the stronger and more arrogant the created version of himself will be.
Multi-cell Sperm (多細胞精子, Ta Saibō Seishi): A fusion of any number less than ten trillion cells that combine. The strength of this form has yet to be observed as the only Multi-cell Sperm observed was quickly taken out by Tatsumaki.
Augmented Strength: His strength was presumably augmented, but it was not shown due to Tatsumaki eliminating it instantly.
Augmented Speed and Reflexes: His speed and reflexes were presumably augmented, but they weren't shown due to Tatsumaki eliminating it instantly.
Augmented Durability: His durability was presumably augmented, but it still wasn't enough, as Tatsumaki was able to nearly effortlessly eliminate it.
Golden Sperm is born
Golden Sperm (黄金精子, Ōgon Seishi): This state requires at least ten trillion cells to create. This form vastly increases his powers to amazing heights and he is able to defeat an injured Tatsumaki, as well as temporarily fight with evolved Garou, something none of the other S-class heroes could do. Sweet Mask went so far as to comment Golden Sperm was beyond his abilities, and that even if all the S-class heroes ganged up on him, it would be a very difficult fight.
Augmented Strength: As Golden Sperm, he was powerful enough to partially penetrate through Tatsumaki's barrier as well as cause great destruction and destroy nearby rocks in his battle with Garou.
Augmented Speed and Reflexes: Golden Sperm is so fast that he was easily able to blitz Tatsumaki in a split second with no visible effort. He is also so fast that he was able to keep up with Garou's speed, with none of the conscious S-class heroes being able to see their fight.
Augmented Durability: Golden Sperm has incredible durability, as he remained unfazed when Tatsumaki attempted to break his neck, and was also able take several attacks from evolved Garou and continue fighting.
Psychic Resistance: Golden Sperm is able to very effectively resist an injured Tatsumaki's psychic attacks with very little effort. However it has been confirmed that if she were at full power, he could lose.[3]
"Do you still think you can win? I am a countless number of "me" merged into one entity. No matter how you cut or tear, how you strike, crush, twist, I'll keep multiplying."[4]
The following section contains Webcomic spoilers. You have been warned, manga-only readers.
"All heroes except Tornado, please form a line and wait for your turn to be killed."
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