Empty Void

The Ninja Village Leader is the founder of the secret Ninja Village. The founder's real name is unknown; the ninjas from the village simply refer to him using pronouns.

Appearance
The Ninja Village Leader has a monstrous appearance with spiked skin and flamed hair. He has different skin colors on different parts of his body. His teeth are all razor sharp.

Personality
The Ninja Village Leader is an utterly ruthless, malevolent, cunning, bloodthirsty and despicable individual. Having been alive for more than three hundred years, he has used his powers and skills to assassinate hundreds of thousands of people over his lifetime. He is the founder of the Ninja Village and starter of atrocious regiments children are put through, and even after founding the village, he continued to assassinate people. When killing his targets, if he comes across people with strong bodies, he will take their bodies away to (presumably) use their body parts to stay young and fresh.

He also did not seem to care about the ninjas who banded together for him, as he merely observed Flashy Flash and Speed-o'-Sound Sonic kill all of the members of the Heavenly Ninja Party from a rooftop. He is also very arrogant, as he challenged the top S-Class hero Blast to a fight and was defeated by the hero, being put in a coma for 15 years.

History
The Ninja Village Leader was born about three hundred years ago, although it is unclear whether he was born a mysterious being or gradually became a mysterious being. Since that time, he honed his skills and started his career as an assassin. His unbelievable power and skills allowed him to reach the top of the assassination industry and give him enough ties to rule the world in the shadows. During this time, he killed several high-profile individuals whose names would be passed down in history.

Because of this, the Ninja Village Leader was regarded as the most powerful ninja to walk the Earth. Sometime in the past, he founded the Ninja Village. The village trained ninja assassins and sent them to factories of the underworld.

Sometime later, the Ninja Village Leader challenged Blast, but he was defeated and put in a coma. The village placed him in a recovery capsule where he layed dormant for 15 years.

Ninjas Arc
After Sonic is once again defeated by Saitama and is recovering, he is approached by the Heavenly Ninja Party. This party consists of ninjas from previous graduating classes of the village, including Gale Wind and Hellfire Flame. They tell Sonic that "he" is almost awake, and reveal to Sonic their plans to kill Flashy Flash and Blast, make the leader of the Ninja Village their leader, and come out of the shadows to take over the world with their superior ninjutsu skills. After Sonic and Flash kill the entire Heavenly Ninja Party, he is revealed to have been observing the battle go down from a nearby rooftop.

The two later arrive at Sonic's residence, where they find Saitama, sitting over a hole in the ground and holding the Ninja Village Leader's equipment. Saitama explains that the Ninja Village Leader approached him and monologued about his legendary demon blades and his immense power. He then attacked Saitama, who easily defeated him with a single downward punch, and was stripped of all of his weapons.

Abilities and Powers
While his fighting abilities have not been shown, it is safe to assume that the Ninja Village Leader is an extremely powerful opponent. Gale Wind claims the Leader has a body count in the 6 figures, and that he is responsible for the deaths of many well-known historic individuals. He stood at the top of the assassin industry and ruled the world from behind the scenes. He is regarded as the most powerful ninja to ever walk the Earth by all the ninjas who graduated from the village, indicating that he possesses S-Class level abilities. This is also shown with the fact that one of his scrolls contains a technique that Flashy Flash used to instantly kill Heavy Smoker, a Dragon-level threat that was shrugging off attacks from Tanktop Master. Gale Wind has described him as possessing overwhelming power, and even after seeing Flashy Flash and Speed-o-Sound Sonic's abilities, he was still confident neither of them would stand a chance. Furthermore, Gale Wind even stated that even if all of the ninjas attacked him together, the leader could handle them as if he were handling an infant.

Despite his amazing power, he was still not strong enough to defeat Blast, the highest-ranking S-Class hero, and was put in a coma by him for 15 years.

Physical Abilities
Immense Strength: The Ninja Village Leader naturally boasts impressive strength, and according to Gale Wind, could kill both Flash and Sonic with ease.

Immense Speed and Reflexes: As the founder of the Ninja Village, the leader has amazing speed and reflexes. According to Gale Wind, he can perform humanly impossible ninjutsu moves four to five times in 0.2 seconds, and even if all of the Heavenly Ninja Party members attacked him at once, the leader would be able to handle them all as if he was handling an infant.

Enhanced Longevity: According to Gale Wind, whenever the Ninja Village Leader found a strong and healthy body, he would take all their blood and innards away from the scene to replace his organs or consume it.

Multiple hearts: Gale Wind states that he has multiple heartbeats, indicating that he has more than one heart.

Fighting Style
Ninjutsu Master: Being considered the strongest ninja to have ever lived, he is highly skilled in Ninjutsu. He is evidently proficient in the use of an absurd variety of weapons, and carries them into battle.
 * Sky Ripping Scattered Flash Slash (裂空散閃斬, Rekkū Sansenzan): The Ninja Village Leader creates powerful hurricanes which he can control by spinning his sword at incredible speeds. Though he's never been seen using it, it can be implied that he can use this technique, since he carried the scroll that detailed how this move is performed.
 * Speed of Sound Electric Discharge Fist: The Ninja Village Leader extends his finger and pokes his opponents on the head, unleashing powerful shots of electricity and killing them. Though he's never been seen using it, it's also implied that he can use this technique since he carried another scroll that detailed how this move is performed.

Equipment
Swords: The Ninja Village Leader carries two swords on his back. According to Saitama, he calls them "Legendary Demon Blades."

Shuriken: He also carried a variety of shuriken, with many different styles among them.

Kunai: A set of Japanese knives which are common ninja weapons.

Stun Gun: An electroshock weapon for disabling attackers.

Scrolls: He has several scrolls on him. They appear to contain the details of several forbidden techniques, as Flashy Flash took some of the scrolls left behind by him and learned a new technique.

Baton: A short bludgeon commonly used by police officers.

Pistol: Among the numerous weapons in his collection is a handgun, with two extra magazines.

Taser: A short-ranged variety of electroshock weapon.

Trivia

 * The mysterious Ninja Master's tendency of harvesting the bodily remains of felled enemies and grafting them to his own flesh parallels the practices of Kakuzu from Masashi Kishimoto's Naruto series. Kakuzu was a super ninja who would harvest the hearts of defeated shinobi and implant them into himself granting him a form of advanced longevity.
 * At some time in the past, while Blast was searching for a mysterious cube, there was a partner of his that carried two swords on his back resembling the Ninja Village Leader.