Isamu/Synopsis

History
Sometime prior to the original storyline, Child Emperor worked as Metal Knight's assistant. He also fought and defeated all of Disciples of Atomic Samurai.

Alien Conquerors Arc
Child Emperor is first seen during the S-Class heroes meeting and was slightly upset that he couldn't meet Blast, who hasn't attended. During the meeting, Sitch explained the prophecy Shibabawa made before her death, but Child Emperor didn't believe it so tried to leave. He was in return mocked by Sitch, stating that Child Emperor is nothing more than a child if he does not comprehend the danger of this matter, which angered him. After the Dark Matter Thieves attack A-City, Child Emperor suggests that the Hero Association should confirm who the enemies are and whether they are what the prophecy was referring to. He later goes to the roof of the Hero Association Headquarters with Genos, Superalloy Darkshine, Tatsumaki, and King. He immediately starts thinking about ways to take care of the spaceship, while Bang, Metal Bat, Atomic Samurai, and Puri-Puri-Prisoner take care of Melzalgald. While using his laptop, Child Emperor warns the Hero Association staff about the about rising energy in the ship. Afterwards, Child Emperor appears beside Genos and Drive Knight, with the latter informing his leave.

Super Fight Arc
Child Emperor uses Underdog Man No. 22 to analyze Eyesight's poisons to find a cure for the paralysis. Child Emperor then proceeds to detonate Underdog Man No. 22, but that did not successfully kill Eyesight as she hardened her skin. Eyesight then manages to find Child Emperor, but is interrupted and eaten by Pig God. Pig God decides to go after the other monsters in Y-City afterwards.

Original Webcomic
Upon the request from Sitch, he tracks down the Monster Association's base in Z City and mentions they could be holding a child hostage. He accompanies the other S-Class heroes against the Monster Association. He plans out how to defeat the Monster Association, particularly Black Sperm with King after Tatsumaki is defeated. Child Emperor gets punched in the gut by Garou.

Fall of Hero Associations Arc
By the time the Hero Association is about to fall soon enough, Child Emperor becomes delusional over adults, such as his idol, Blast and his mentor, Bofoi, are not coming to help Child Emperor and their fellow heroes during the Monster Association incident on their final battle against Garou. Thus, determined to be strong without needing help from them or anyone.