Another possible storyline is a love triangle between a Saitama Highschool student, a character from DxD, and another student from their own school. This would add an element of drama and emotion to the fanfiction, as they navigate their feelings while also dealing with the supernatural elements of the DxD world.
Issei Hyoudou is often a popular character. His charisma and his journey of becoming stronger in the DxD world make him an interesting addition to any Saitama Highschool DxD fanfiction. He can bring his unique skills and experiences to interact with the highschool setting.
Tornado of Terror would likely be one of the first to try and take on Evil Saitama. She's powerful and confident, but she would soon realize the extent of his power. Mumen Rider, despite being weak, would still stand up to Evil Saitama out of a sense of justice. He would be quickly defeated but his act of courage might inspire other heroes to step up.
The characters in DxD would be quite shocked at first. Ichigo's appearance and his powers are so different from what they are used to. For example, Rias Gremory would probably be intrigued by Ichigo. She might try to form an alliance with him, seeing his potential as a powerful ally. Issei, being the main character in DxD, would likely be both jealous and in awe of Ichigo's abilities, and might challenge him at first but then learn from him over time.
When it comes to a fanfiction about Saitama's training days, it has the potential to be really engaging. We could see the evolution of his training methods, perhaps from simple exercises to more complex and extreme ones. It might also explore his interactions with the people around him during that time, if there were any. For example, did he have any mentors or friends who supported or doubted him? This kind of fanfiction can add a whole new layer to Saitama's character and make us appreciate his journey to becoming One Punch Man even more.
Saitama is a very powerful hero in the One Punch Man universe. He can defeat any opponent with just one punch. He has a simple appearance and a somewhat laid - back personality.
Issei would probably be the first to want to fight Thanos. He's always eager to prove himself and protect his friends. He might initially underestimate Thanos due to his own growing power and confidence, but soon realize how powerful Thanos really is. Rias would be more cautious. She would likely try to gather information about Thanos first and then formulate a plan to either fight or negotiate with him.
Issei, being the hot - blooded character he is, would probably be excited to meet someone as powerful as Naruto. He might challenge Naruto to a friendly spar at first, hoping to learn from him and test his own strength. And as he gets to know Naruto better, he could start to see him as a brother - in - arms, especially if they face common enemies together.
The villains would have a mixed reaction. Some of the more power - hungry ones might see this as an opportunity to join forces with Saitama and cause even more chaos. However, there would also be villains who are afraid of Saitama's power, even if he's on their side now. They would be worried that he could turn on them at any moment. Overall, Saitama turning evil would completely disrupt the existing power dynamics in the One Punch Man world.