Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
Character development is also crucial. In many such fanfictions, Female Goku Black may start as a villainous or at least antagonistic character. But as the story unfolds, she might change due to her interactions with Goku. This transformation can be really interesting to follow. For example, she could start to question her own motives or even develop feelings for Goku, which is a big shift from her initial stance.
One popular 'goku x female goku black fanfiction' might be 'The Unlikely Bond'. It explores a unique relationship between Goku and Female Goku Black. In this fic, they start off as enemies but gradually discover they have more in common than they thought.
In some versions, the female Goku could be part of a prophecy. The two Gokus meet, and at first, there is some confusion and misunderstanding. But as they get to know each other, they discover that they are key to fulfilling the prophecy. They combine their powers and defeat an ancient evil that was threatening both of their worlds.
Honestly, comparing the strength of anime Goku and manga Goku is tricky. Both versions have their unique strengths and challenges depicted differently, making it hard to make a clear-cut comparison.
In general, it's a bit of a toss-up. The strength of Manga Goku and Anime Goku can vary depending on the specific arcs and battles. Sometimes, it might seem like one is stronger in a particular situation, but that could change in another.
One idea could be that the female Saiyan is from a different part of the universe. She's heard tales of Goku's power and comes to Earth to challenge him. But when she meets him, she realizes he's not just about power but also has a kind heart. So instead of fighting, they start training together.
One common theme is the power - dynamic. It often shows how a female character interacts with Goku's extreme power. For example, she might be in awe of it at first and then strive to reach a similar level.