For Sirius, it could be a huge shock. He might feel both betrayed as a member of House Black and also conflicted because he had some connection with Tonks. He would start to question his own judgment of people.
The other members of House Black would likely be furious. They would see Tonks as a traitor and might seek revenge. This could lead to a lot of tension and dangerous situations for Tonks. They might also use their influence to turn other people against her.
One possible motive could be love. Maybe she fell in love with someone who was an enemy of House Black and chose that person over the loyalty to the house. For example, if she was in love with a member of the Order of the Phoenix who was against the dark ways of House Black.
If Naruto and Sakura betrayed, their closest friends like Sasuke would be deeply affected. Sasuke, who has a complex relationship with them, would be in a state of shock and confusion. He might initially try to find out the reasons behind their betrayal and could even be torn between loyalty to the village and loyalty to his friends.
It can add drama. Tonks might start acting out of character, being more cold or distant towards Hermione or even Remus. This can create tension in the relationships. For example, she might try to sabotage their friendship by spreading rumors or trying to keep them apart.
It can also change the power dynamics. Spider - Man might become more isolated and have to rely more on his own wits and skills without the Black Cat's support. This could lead to him developing new abilities or strategies in the fanfiction. For example, he might have to form new alliances or learn to fight in different ways.
Time travel for Harry could be a way to confront his past traumas. He might go back to a time when his parents were alive and get some closure. This could make him more at peace with himself and less haunted by his past. As for Tonks, time travel could expose her to different forms of magic and different social structures. If she travels to a time when pure - blood - supremacist ideas were more prevalent, she could become more of an advocate for equality. She might also see how her family has evolved over time, which could give her a stronger sense of identity and purpose.
Well, her possessiveness might isolate Harry in a way. He may feel smothered by her actions, which could cause him to rebel or try to distance himself. This creates a new dynamic in the story where Harry's actions are influenced by trying to break free from Tonks' possessive hold, and this can lead to all sorts of plot developments like him making unwise decisions on his own or seeking out other allies who are more understanding.
It can shatter the family structure. The trust between the couple is broken, which can lead to arguments, separation or divorce. If there are children involved, they may become confused and traumatized by the sudden change in the family dynamic.
Tonks' sense of adventure and her Metamorphmagus ability combine to make her a really interesting character in these fanfictions. She might use her ability to explore the old Black family mansion in ways others can't. And she'll be eager to share her discoveries with the family, whether they like it or not. This can lead to some hilarious or tense moments depending on the reactions of different Black family members.
It could make Sebastian, Ciel's butler, more protective. He might see Elizabeth as a potential weakness for Ciel, or he could also view the relationship as something that could be used to further Ciel's goals. For example, if there are other noble families involved, Sebastian could manipulate the situation based on Ciel and Elizabeth's new - found closeness.
Some characters might be afraid of Naruto if he has black chakra. For example, his friends like Sakura and Kakashi could be initially cautious around him. They might not trust this new, unknown aspect of his power. Sakura might worry that the black chakra could harm Naruto himself, while Kakashi would be on high alert to make sure Naruto doesn't lose control.