It might be an abbreviation for a name, like 'David X. Doe' or something similar. Or it could be a unique name within a specific group or community that is into fanfiction. Maybe it's a code name for a person who reviews fanfiction. Without more context, it's really hard to say for sure.
Issei would be a popular choice. Since he is the main character in the original series, having him time travel would create many interesting storylines. He could use his knowledge of future events and his growth as a character to change things in the past.
Well, in some fanfictions, Issei travels back in time and tries to change the fate of the entire supernatural world. He realizes that some of the prophecies and events that are set to happen are actually going to lead to a much darker future. So, he goes back and starts influencing key figures in the supernatural community. He might teach some of the younger devils new techniques or give advice to the leaders of the different factions. This not only changes his own future but also has a ripple effect on the whole world of DxD, creating a completely different timeline with new challenges and opportunities.
One idea could be that Issei goes back in time to his first day at school and uses his future knowledge to avoid all the initial embarrassments. He could also try to prevent some of the early battles and form alliances earlier.
Soaring Soldier City was an important character in " Demon High DXD " who had the ability to stop time. According to the novel, this ability came from the mysterious organization he was in, the Hand of Time. This organization had the ability to control time and passed on their power to others so that they also had the ability to stop time.
The reason why Soaring Soldier City had the ability to stop time was because he had received the power from the Hand of Time. The speed and direction of time flow on his body had been changed, allowing him to stop time under certain circumstances. This ability was very important to Soaring Soldier because he could use it to solve many problems such as avoiding danger, stopping the enemy's movements, and so on.
The concept of time manipulation through chrono vision in DxD fanfics can also be related to character development. A character who initially misuses the power, perhaps by relying too much on it and not developing other skills, could face a setback. For instance, they might encounter an enemy who can disrupt their chrono vision. This would then force them to grow and adapt, learning to fight without relying solely on seeing into the future, which makes for an interesting character arc.
You can try websites like Fanfiction.net. It has a large collection of fan - made stories for various series, including Highschool DxD. Just search for 'Highschool DxD Vali' and you'll get a list of relevant fanfictions.
One popular fanfiction might be those that explore Vali's backstory more in - depth. For example, stories could detail his training and how he became so powerful.
To develop the male OC, start with his backstory. He could be from a family with a long - lost connection to some powerful time - based magic. This gives depth to his character. In terms of his personality, make him a bit of an outcast at first because of his strange power. But as the story progresses, he learns to embrace it. His relationships should also evolve. He might start off being bullied by some of the more powerful characters in the Highschool DxD world, but as he gets better at using his time - stopping ability, he gains respect and forms new friendships. You can also add some flaws to his character, like being a bit too impulsive when he sees an opportunity to use his power for good, which sometimes gets him into trouble.
A really interesting plot would be if the male OC's time - stopping power has a limit. He discovers that every time he uses it, it drains his energy and he has to find ways to replenish it. This could lead to him having to make difficult choices about when and how often to use his power. Maybe he has to form an alliance with a magical being that can help him manage his power in exchange for some favors. And all this while, he's also dealing with the normal high school drama in the DxD universe like dealing with rivalries and making friends.