Isamu/Other Media

Numbers
At Y-City, Child Emperor is working on a new invention, "Okame-Chan", which scans the body for muscle mass and the development of nerves, balancing it out with the target's weight to determine the strength of the target's body.

After testing the new invention, a monster alert sounds. Child Emperor and other heroes try to stop Jumping Spider together, but all of them are easily blown away by the creature except Child Emperor. Jumping Spider is later defeated by Saitama, but King is given the credit. Child Emperor takes the opportunity to measure the strengths of the heroes that have just arrived. When Child Emperor tries to measure Saitama's strength, the invention cracks and calculates Saitama's strength as undefined. Child Emperor misinterprets this reading as Saitama being extremely weak. On the other hand, King's strength is also undefined. Bang refuses to get measured, Genos is not able to be measured due to his robotic parts, and Fubuki gets a low rating.

One-Punch Man Holiday Special Chapter
When asked what his plans for Christmas are, Child Emperor says he got invited to a lot of parties by his classmates, but complains that he won't have time for research.

Owned Items
Various members of the Surface Team are discussing the items they use for fighting monsters. They are disrupted by Flashy Flash who tells them to stop chitchatting and instead concentrate on the mission.

The Murder Case That Is Too Impossible
Child Emperor and other S-Class heroes are invited to a hot spring resort, after the Dark Matter Thieves failed invasion. After the hot spring, Sitch gathers all the heroes into a celebration of the victory against the invasion. Some heroes become drunk after drinking the sake and disgust Child Emperor. Child Emperor makes small talk with Zombieman about whether or not he is enjoying himself. The next day after the ceremony, the heroes find Zombieman murdered, stabbed in the back by Atomic Samurai's katana. Child Emperor states that one of the S-Class heroes is the culprit. As he investigates the murder, he gathers evidence and information from the heroes and tries to eliminate suspects in order to find out the truth. He interrogates all, including Saitama and finally King, but is scared off by his King Engine. When progress halts, Tatsumaki tries to restrain everyone, when Zombieman suddenly wakes up. Zombieman reveals that Atomic Samurai's katana was floating with green light surrounding it similar to Tatsumaki's when it stabbed him. Child Emperor questions Tatsumaki, but she angrily denies it. Zombieman says he simply does not care about what happened the night prior and the heroes disband and the case is dropped.

Later, Child Emperor is called by Sitch to look at the surveillance camera footage of last night. It is shown that Tatsumaki did in fact stab Zombieman, while heavily drunk.

Zombieman Murder Case 2
Child Emperor, Zombieman, Superalloy Darkshine, and Metal Bat are dispatched to a forlorn, snowy mountain to hunt a monster. They fail to find anything, so they check into a lodge for the night. There they meet Saitama and Genos, who also got stuck on the mountain and had to check in, and Flashy Flash, who is trying to relax on a vacation.

Later, in a brief fight between Speed-o'-Sound Sonic and Genos, the power goes out, followed by a sudden explosion. The heroes grab a flashlight and head to the den, finding the room destroyed and Zombieman unconscious. Child Emperor can't locate any external heat signatures, so he deduces that the culprit must be in the lodge. After recovering, Zombieman tells them what little he knows, and Sonic enters the room to prove his innocence. The group finds that they all have good alibis, completely forgetting about Flashy Flash upstairs. They assume the monster must be responsible, but after the Hero Association tells them it is just a bear monster called Bruinado, they decide it can't be.

Once Child Emperor sees Saitama sneeze again, he deduces the following: the abundance of heaters in the lodge dried out the interior, Genos and Sonic's fight kicked up flammable dust, Saitama's sneeze pushed the dust into the den, all the electricity being used caused a breaker to trip, and Zombieman's lighter caused the dust to detonate. The group is relieved at the conclusion.

Suddenly, Bruinado crashes through the front door - however, he is quickly defeated by the abundance of S-Class heroes. Upstairs, Flashy Flash continues to use all the lodge's power as he relaxes.

One Punch Man: A Hero Nobody Knows
Child Emperor is a playable character in the video game, One Punch Man: A Hero Nobody Knows.