Serpenters

Serpenters (サーペンターズ) are a villain duo comprised of twin brothers Ena (エナ) and Dio (ディオ). They work for Flect Turn in My Hero Academia: World Heroes' Mission.

Appearance
The Serpenters are men of average build and fair skin with bowl-cut indigo hair, yellow reptilian eyes with dark purple markings surrounding them, and a set of large fangs.

Each of them wear a simple red and white tunic with gray, presumably snake skin, boots.

When boosted by Trigger, they become more vicious and snake-like. Markings appear on their faces, their hair flares up becoming spiky, their mouths stretch to their ears and their teeth grow sharp.

Personality
The Serpenters' personalities are exactly alike, both are devoted to carrying out Flect's plan. They joined Humarise's cause despite having Quirks so that they would be spared from the genocide on Quirk users.

They are very erratic and excitable, eager to fight and kill any opponent they face, laughing maniacally all the while.

My Hero Academia: World Heroes' Mission
The anti-Quirk terrorist organization known as Humarise commits a terrorist bombing that causes the deaths of thousands of people by setting off a Trigger Bomb in a city. In response to this terrorist attack, the World Heroes Association organizes an international operation to raid all the branches that Humarise has in the world in an effort to defeat the terrorist organization. Although the raids were successful across the world, each task forces were unable to locate the bombs or apprehend the leader Flect Turn.

Days later, Humarise hijacks all telecommunication and announces globally that they have placed the Trigger Bombs in twenty-five cities around the world, and that they will explode in less than two hours. To further attract the greatest number of heroes to the prepared trap, they indicate in which cities are found. Their ultimatum causes widespread panic throughout the twenty-five countries, so the WHA gives the Heroes the greenlight to scramble in defense to quell the mass hysteria and locate the Trigger Bomb.

One by one, the Heroes in each sector engage in a all-out war against the Humarise sleeper agents guarding the bombs, delaying their effort to stop the detonation. Just when Flect Turn was confident of his assured victory, their scouts reported a charter plane piloted by Rody Soul heading toward their location, carrying the Endeavor Agency interns from the Otheon Task Force: Izuku Midoriya, Shoto Todoroki, and Katsuki Bakugo.

Realizing that the young heroes are coming to foil his plot, Flect Turn orders Leviathan and the Serpenters to go out there and deal with these intruders. After the young heroes launched a direct assault on the main Humarise headquarters, Katsuki stays behind to deal with the Serpenter Twins while Izuku and Shoto breach further inside to disable the Trigger Bombs.

Katsuki asks why someone like one of the Serpenters is a follower of Humarise since he has a Quirk. The villain replies that "they" have been chosen to live in the new world Humarise will create with the upcoming Quirk genocide, revealing the presence of his twin brother. Katsuki points out that they are just optimistic cowards trying to save their own lives, before attacking them with a flurry of blasts. Using their extendable blades, the twins dash in opposite directions, easily dodging Katsuki's shots before striking back. The Sword Kill of one of the siblings manages to overcome Katsuki's defenses, while those of the other twin manage to slash him, giggling maniacally at his achievement.

Despite his injuries, Katsuki continues on the offensive, but this time with more powerful blasts of AP Machine-Gun. However, the twins can cut through even the explosions with their blades, and surround Katsuki while laughing at him endlessly. Unable to bear being shot down, he readies the grenades from his equipment before lunging at the siblings, who quickly evade him by swinging past the massive columns and facade of Humarise's base.

Katsuki chases after them, while shooting at them with his Auto-Cannon, but thanks to their speed and agility, the Serpenters manage to avoid being hit by the shots. Katsuki tries to attack one of them at close range, but is skewered by the other twin's blades, who taunt him. Katsuki shoots and manages to get behind him, but when he is about to attack, he has to jump back to avoid the other brother's Sword Kill. Katsuki and the Serpenters take the battle back into the air, fighting around one of the columns, until the twins manage to outclass Katsuki and slice his back, laughing at him. However, they didn't realize that Katsuki had outsmarted them.

Knowing that he couldn't outmatch them, as he chased the twins through the great colonnades of the entrance, he stocked up some of his grenades on the column. With the trap set and his enemies off-guard, Katsuki pulls out the pin of one of his Grenadier Bracers to fire at the column, causing a chain of explosions that reduces it to rubble, collapsing onto them. Unfortunately, the Serpenters inject themselves with Trigger to break out of the rubble, gaining more speed, strength, and being able to generate even more whip blades. With both their physical abilities and Quirks empowered by the drug, they continue fighting him.

Katsuki can barely stand up to them. He is unable to hit any of the Serpenters with his shots, while they easily overwhelm him slashing and slicing him mercilessly. Still, he keeps on pushing until he manages to trick them. After the twins stick their blades into him, Katsuki grabs hold of their appendages, and without letting them go, he uses his Explosion Quirk to propel them all together, taking advantage of the centrifugal force to slam them against the cavern wall.

With the twins trapped on the wall, Katsuki fires both his Grenadier Bracers at them. The Serpenters generate Sword Kills through their mouths to destroy gadgets before they reach them, but the resulting explosion only further pins them to the wall. Completely immobilized and defenseless, all they can do is watch as Katsuki defeats them with his Ultimate Move: Howitzer Impact. The attack is so powerful that it reduces the entrance to rubble, leaving the Serpenters trapped under the debris.

Izuku and the other trainees were successful in defusing all of the Trigger Bombs, and defeating Flect Turn and the higher-ranking members of Humarise in the process. With the terrorist plot foiled, all the surviving Humarise members are arrested and the Trigger Bombs are safely removed.

Abilities
Overall Abilities: The Serpenters were an incredibly dangerous pair with an undying lust for battle and masterful handling on their Quirk. Their combined might is used to overwhelm and surprise opponents with swift and powerful strikes that slice their opponents apart while grappling with their swords to maneuver in the air. Their skill allowed them to overwhelm and contend with Katsuki, one of Class 1-A's most powerful students, and almost kill him upon utilizing Trigger.

Agility: Both the Serpenter Twins are very agile opponents, enabling them to even keep up or surpass one of Class 1-A's agile students, Katsuki and his Explosive Speed. With Trigger, this agility is temproarily increased by ten-folds, making them outclassing Katsuki.

Quirk
Sword Kill (ソード・キル): Both brothers have a Quirk that allow them to transform their arms into extendable bellow swords that can be used to attack and grapple. When boosted by Trigger, they are able to create seven at a time, an additional four from their upper back and one from their mouths.

Trivia

 * The Serpenters are referred to as the Twin Villains (双子ヴィラン).