Sidero

Sidero (シデロ) is a villain working for Flect Turn in My Hero Academia: World Heroes' Mission.

Appearance
Sidero is a tall man with slicked back brown and black hair, an extremely wide mouth, and large bulbous elbows.

He wears a gray combat suit of similar design to Rogone and Beros', though his version has sleeves going to his upper arm. Accompany his suit are cream-colored boots, and pale gold horned mask that obscures the upper half of his face. All of his fingers barring his thumbs have black iron balls on his knuckles.

Personality
Like most Humarise members, Sidero is devoted to carrying out Flect's plan. Although he presumably only joined the cult to avoid being killed for having a Quirk, as he was quick to offer information once captured by Heroes.

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 organize an international operation to raid all the branches that Humarise has in the world in an effort to defeat the terrorist group.

Scientist Alan Kay escapes with a briefcase of important information and it ends up in the hands of Izuku Midoriya and Rody Soul. After putting the both of them on the Otheon most wanted list, Flect Turn sends Beros and Sidero to capture the boys. Since they are planning to escape Otheon authorities by crossing over to the Otheon-Klayd Border, Sidero and Beros board a helicopter to pursue them.

Just as Izuku and Rody reach the Klayd border, Beros and Sidero confront them in the helicopter. Beros starts shooting arrows at them with her Longbow Quirk, but Izuku is able to quickly evade the projectiles, despite his injuries and having to carry Rody. Sidero suggests Beros to uses his Iron Balls instead. Accepting his suggestion, Beros uses her Longbow to fire the metallic spheres at Izuku and Rody. The projectiles increase in mass and size considerably before impact, causing great destruction to the canyon walls, which is witnessed by people on the border.

Although the shots fail to hit Izuku, they do manage to make him lose his balance and fall. Izuku manages to use Blackwhip to latch onto the tail of the helicopter, attacking it with a Delaware Smash Air Force, causing the pilot to lose control of the rotorcraft. The recoil of the attack causes Izuku and Rody to fall roughly to the ground, although fortunately they only get bruises.

Sidero jumps out of the helicopter and lands right in front of Rody, ready to kill him with another one of his giant metal spheres. Despite the dire situation, Rody throws the briefcase at Izuku, but Beros shoots several arrows at the young hero to prevent him for helping. Sidero is about to crush Rody just as he begins to fall off the cliff.

Fortunately, Shoto Todoroki and Katsuki Bakugo were at the border when the battle began, and seeing its destruction, they rushed to help. Shoto uses his Quirk to generate a large wave of ice that not only captures Sidero but also saves Rody's life. From the helicopter, Beros begins attacking Shoto with her arrows, but is interrupted when Katsuki appears and fires AP Shot: Auto-Cannon at her, damaging the chopper.

The trapped Sidero is willing to surrender to Shoto in exchange for telling him everything he knows about Humarise and the briefcase, but Beros shoots several explosive arrows at him to punish him for his betrayal. After this, she continues facing Katsuki, who chases the helicopter through the air using his Explosions to propel himself and move through the air. Thanks to the great skill and control he has over his Quirk, Katsuki manages to dodge and destroy all the arrows she fires at him, until her quiver is empty.

Katsuki reaches the helicopter and orders her to surrender, since she is out of arrows plus the chopper is out of control due to the damage received during the battle. Finding herself cornered, Beros picks death over being captured and interrogated by the Heroes. She proclaims her allegiance to the cause of Humarise and jumps out of the helicopter into the chasm, right before it crashes. After Beros' death, Sidero was captured and arrested while the trainees and Rody escape through the border.

Abilities
Overall Abilities: Sidero is considered to be a mercenary for fire as he was able to throw Izuku and Rody out on the cliff. He seems to be specialized in long-range attacks before he expands his iron balls to create devastating attacks.

Quirk
Iron Ball (アイアン・ボール): Sidero's Quirk allows him to create and detach iron balls from his knuckles, which he can then enlarge in size and mass. He can detach them to provide ammo for Beros' Quirk.

Trivia

 * He is referred to as the Iron Ball Villain (鉄球ヴィラン).
 * Sidero's name could be derived from the Greek word "Sídero" (σίδερο), which translates to "iron," befitting the iron attribute of his Quirk.
 * Sidero shares his Japanese and English voice actors with other characters.
 * His Japanese voice actor, Yuichiro Umehara, also voices Katsuki Bakugo in the VOMIC.
 * His English voice actor, D.C. Douglas, also voices Untenmaru Kurumada.
 * Sidero was a security guard for a VIP before being recruited into Humarise.
 * Sidero shares his birthday with David Shield and Mitsuki Bakugo.