The first obstacle could be the time - travel process itself. Sonic might experience some sort of disorientation or time - related anomalies. For example, he could end up in the wrong time period initially. Another obstacle is that he may face enemies in the past that are more powerful or different in nature compared to the ones he knows in his own time. Also, he has to make sure that his actions in the past don't create more problems in the future. If he changes too much, it could have unforeseen consequences for the world he left behind.
In this fanfiction scenario, Sonic would likely face the obstacle of being recognized as an outsider in the past. This could lead to him being hunted or distrusted by the inhabitants of that time. Additionally, he may not have all of his usual resources or powers available to him in the past. For instance, if his time - traveling disrupts his connection to the Chaos Emeralds, he'll have to find alternative ways to fight. And of course, there's the challenge of actually finding Shadow in time. The past is a big place, and Shadow could be anywhere, in any kind of danger.
Well, it could be that Sonic goes back in time because Shadow is in a dire situation that only Sonic can prevent. This could be due to a threat from a powerful villain that managed to overpower Shadow in the past. Sonic, being the hero he is, decides to take the risk of time travel. He might have to use some sort of time - traveling device or power. Once in the past, he'll need to quickly figure out how to stop the threat before it's too late. This fanfiction idea is really cool as it combines the action - packed nature of Sonic's world with the concept of time travel.
One potential plot could be Bloom going back to the time when the first great war in the magical world happened. She could try to stop the war from starting, which would change the entire history of the magical world. This would also mean that the relationships between different magical species would be completely different in the present.
One popular fanfiction with this plot is 'Time's Redemption'. In it, Hermione uses a powerful time - turning device to go back. She faces many challenges in the past, like avoiding detection by other characters while trying to figure out how to prevent Fred's death. It's a great read for those who love emotional and action - packed stories.
She could accidentally change other things in the past. For example, her presence might disrupt some other events that were supposed to happen. Maybe she prevents another character from getting a crucial piece of information, which then has a ripple effect on the future.
Well, perhaps Lilly realizes that Sev is in some sort of danger in the past that leads to a tragic end in the future. So she uses a magical device or spell to travel back in time. Once there, she has to find Sev among all the chaos and danger. Maybe she has to disguise herself to fit into the time period. Then she'd try to prevent the event that would have doomed Sev.
One great fanfiction with this plot is 'Time's Redemption'. In it, Harry uses a powerful time - turning spell he discovers in an ancient book. He has to face many challenges in the past, like avoiding detection from the Ministry's time - turner regulations. Another good one is 'Back to Save Sirius'. Here, Harry teams up with Hermione and they use a secret time - travel device left by Dumbledore.
Obviously, Yusei himself. And his friends from his original time period might also show up in flashbacks or if he somehow brings them back in time with him. For example, Jack could be there.
Obviously, Josuke himself would be the main character. His friends like Okuyasu could also be involved. Maybe Okuyasu somehow follows Josuke back in time or Josuke has to find a way to bring him back if he gets left behind in the past.
One possible plot twist could be that when Lily goes back, she discovers that saving Sev is far more complicated than she thought. Maybe there are forces in the past that are determined to keep the original timeline intact. Another twist could be that in her attempt to save Sev, she accidentally changes something else in the wizarding world for the worse.
Well, perhaps when Fred goes back, he discovers that the danger to Harry is much more complex than he initially thought. There could be a traitor among the people he thought were allies in the past. Also, Fred himself might get stuck in the past and has to find a way to get back while still ensuring Harry's safety. Maybe the time - traveling magic is being manipulated by a hidden enemy, and Fred has to figure out who and how to stop it to save Harry.