Roy Mustang might also be paired with Edward in some fanfictions. They could be on a joint mission in the other world, with Mustang's strategic mind and Edward's combat skills combining to face the new threats. Their banter and the way they work together can be a great source of entertainment and plot development.
Winry Rockbell is often paired with Edward. Their relationship from the original series can be further explored in the alternate world setting. Maybe in this new world, they have different challenges in their relationship, like different social statuses or new enemies that target their relationship.
Alphonse Elric is often present. He might play a role in helping Edward understand and use his new gamer - like abilities in relation to alchemy. For example, he could be the one who discovers a new aspect of Edward's powers.
Obviously, Edward Elric himself is the central character in this type of fanfiction. His brother Alphonse might also be a common character, often trying to help Edward deal with his new situation. Winry Rockbell could be there too, perhaps having a different kind of relationship with Edward now that he is a girl. There might also be the appearance of some of the villains from the original story, who could either take advantage of Edward's new form or be involved in the reason why he turned into a girl in the first place.
One interesting plot could be Edward trying to adapt to a world where alchemy doesn't exist in the same way. He might have to learn new forms of magic or technology to get by. For example, he could struggle with not having his alchemy skills to help him in combat or solve problems at first, but then gradually discovers new powers within himself in this new world.
Obviously, Edward Elric himself is a very popular character. He's the protagonist of the original story and his return is the central theme, so he's always in the spotlight in these fanfictions.
One likely character could be a rival alchemist who is jealous of Edward's skills and reputation. Another might be a villain from the original story who has a grudge against Edward. Also, a new character created specifically for the fanfiction, like a power - hungry alchemist who thinks Edward can help him achieve his goals.
There's a chance that Scar could betray Edward in certain fanfiction concepts. Scar has his own motives and a complex past. If he feels that Edward is getting in the way of his revenge or his understanding of alchemy, he might betray him. Additionally, some fanfictions might explore the idea of an old acquaintance from Edward's childhood betraying him. Maybe someone who was once a friend but has since been corrupted by power or a dark influence. And then there's always the possibility of a new, mysterious character being introduced specifically to betray Edward for some yet - to - be - revealed reason.
Edward might meet his parents. Since he has the chance to go back in time, he could meet them when they were alive and perhaps learn more about alchemy from them, which could change his future actions.
Sasuke is often paired with Itachi in these fanfictions. Their complex relationship from the original Naruto series can be explored in new ways in another world. For example, they might be on a mission together in a world full of unknown dangers. Another popular character to be paired with Itachi is Naruto. Their different outlooks on life and friendship can create interesting dynamics, especially when they are in a strange new world where they have to rely on each other more than ever. Shisui could also be paired with Itachi. Since they were friends in the original story, in the fanfiction, they could be reunited in another world and face challenges together, perhaps against a new and powerful enemy.
Rukia could be a great character to pair with Ichigo. Since they have a strong bond in the original series, in the fanfiction, she could follow him into the other world or be summoned there later. Their combined power and friendship would make for an interesting dynamic as they face new challenges.
Another theme is redemption. Some fanfictions might explore the idea of whether Pride can be redeemed through its interactions with Edward. It could be a complex exploration of good and evil, where Edward's character might influence Pride to change or at least question its own existence and actions.