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.

Monster Association Arc
Child Emperor is investigating the tunnels left by Elder Centipede to locate the Monster Association's base. Bofoi is discussing with Child Emperor and tells him that he will not join in on the operation to raid the Monster Association. He tells Child Emperor that the Monster Association is thoroughly prepared for the Hero Association and that many heroes will be sacrificed in the process. Bofoi tells him that the Hero Association denied permission for him to plant explosives in the designated hideout of the Monster Association headquarters, because saving the hostage was their highest priority. Due to this, Bofoi will not bother with the operation. Child Emperor continues tries to convince Bofoi to partake in the raid but is rejected by Bofoi, who refuses to participate due to other potential threats. Bofoi mentions how Monster King Orochi pierced through the Metal Knight drone before it could activate its self destruction mechanism. Bofoi suggests to Child Emperor to not trust those around him and to accumulate his power as you only need yourself to fight for justice. As a result, Child Emperor tells Sekingar to take Demon Cyborg off the roster due to a suspicious history and Silver Fang due to his past relationship with Garou.

The S-class heroes, Child Emperor, Tatsumaki, Kamikaze, Pig God, Flashy Flash, Superalloy Darkshine, Zombieman, Puri-puri Prisoner and Sekingar attend a meeting and they reassure Narinki that they will rescue his son. They each receive a transmitter that will show their location to each other. They discuss about the situation until Sweet Mask bursts into the meeting. Child Emperor tries to calm him down and get him to accept a leadership role with the surface strike team but he refuses. Child Emperor soon leaves to join the rest of the heroes preparing to leave. He notices King is missing and wonders where he is but is told by Zombieman that he can hear the King Engine. King returns and they all leave to attack the Monster Association.

Monster Association Arc
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.