They could have an adventure where they go on a quest to find a super - powerful, but very elusive monster. Child Emperor uses his gadgets and intelligence to track it down, while Saitama is just there for the ride, ready to punch it when they find it.
Well, it could be that Child Emperor creates some high - tech gadget specifically designed to analyze Saitama. He might think that Saitama is some sort of new type of hero that defies all known scientific principles. Saitama would likely go along with it, as long as there's no trouble and he can still get his grocery shopping done. Maybe they end up teaming up to fight a really tough monster that neither could handle alone, with Child Emperor providing the strategic planning and Saitama delivering the knockout punch.
A plot where Saitama travels to different dimensions in the One Punch Man universe. He could encounter strange versions of himself or other heroes and villains, leading to humorous and action - packed situations.
One way is to explore his life before he became a hero. Maybe he had a normal job and was constantly frustrated with the mundanity of it. This could have been the catalyst for his intense training.
Well, a lot of One Punch Man fanfictions about heroes seeing Saitama are really interesting. Some focus on their initial shock at his power. For example, Genos is always in awe of Saitama's strength in the original work, and in fanfictions, this can be explored even deeper, like how he tries to understand the source of that power.
Child Emperor would likely interact with other heroes in a very intellectual way. For example, with Metal Knight, he might engage in debates about the ethics of using advanced technology in combat. He would probably be in awe of Saitama's strength but also try to analyze it scientifically. When it comes to Tatsumaki, he might be a bit cautious as she can be quite temperamental, but he would still try to work with her by presenting his inventions as useful tools for her powers.
The plot could involve Saitama teaching a group of new heroes how to face their fears. He would tell them about his own journey, starting as an ordinary guy who decided to become a hero just for fun. Saitama could teach them that no matter how strong the enemy is, one should not be afraid to take the first step. He might use his one - punch knockout strategy as a metaphor for facing difficulties head - on, even if it seems impossible at first.
I also like the scenes where Saitama is just casually hanging out with the heroes, and they're trying to figure him out. He doesn't fit into their idea of what a hero should be, and the awkward yet hilarious interactions that follow are a great part of these fanfictions. For instance, he might be eating a meal with them, and they're all secretly observing him, wondering how someone so ordinary - looking can be so strong.
Identity exploration is also a theme. The sister might be struggling with being in Saitama's shadow or trying to find her own identity as a hero or just as an individual. She could be trying to make a name for herself without relying on her brother's fame.
One good fanfiction could be 'Saitama's Sister: The Hidden Power'. It explores the idea of Saitama having a sister with her own set of powers. In this story, she tries to keep up with her brother's reputation while also finding her own place in the hero world.
One fanfiction that's quite popular is 'The Female Saitama's Adventure'. It takes the concept of a female Saitama and puts her in different comical situations in the One Punch Man universe. Another interesting one is 'Female Saitama: A New Hero'. It focuses on how she might interact with the existing heroes and villains in a more character - driven way.