Neville Longbottom might also be a character. Neville has his own connection to the fight against the dark side. He could share his experiences with her and they could bond over their shared desire to break free from the dark legacies of their families. Also, Luna Lovegood could be in the story. Luna's unique perspective on life and magic would be a great contrast to the daughter's more complex family situation, and they could have some very interesting conversations.
Luna Lovegood might be an unexpected character to interact with Regulus. Given her unique perspective on magic and the wizarding world, she could offer him a different view on life after his resurrection. Also, Kreacher, the house - elf who was loyal to the Black family, would surely be involved in his story, as he was very attached to Regulus.
One way this could be possible in fanfiction is through some creative plot twists. Maybe there was a hidden relationship between a relative of Hermione and Regulus. It could involve time - traveling magic that somehow altered the family lines. Another idea is that there was a secret adoption or a magical protection spell that connected Hermione to Regulus in a family - like way.
In this fanfiction concept, it could lead to a whole new set of character dynamics. Hermione's intelligence could be seen as an inheritance from the Black family's cunning. For example, she might discover some long - lost Black family magic that helps her in her adventures at Hogwarts. It could also create interesting interactions with Sirius Black, who was Regulus' brother. Maybe Sirius would be initially shocked but then grow to be very protective of Hermione.
They might start off as enemies. Sirius doesn't get along with his family, so he may not want the Marauders to have anything to do with Regulus. But sometimes, they could end up working together for a common good.
It could contain accusations. For instance, Regulus might accuse Voldemort of betraying the pure - blood ideals he once claimed to uphold. He could point out how Voldemort's actions were actually harming the wizarding world rather than purifying it.
They could interact with a sense of newfound peace. Sirius might be the first to approach Regulus with open arms, ready to forgive all the past. And Regulus would be a bit more reserved at first but then slowly warm up. They might sit together in a beautiful, otherworldly garden and just talk for hours, catching up on everything that happened since they were last together.
In many fanfictions, they interact as kindred spirits. Since they both come from old Slytherin families with a lot of expectations. For example, they might share their fears about the Dark Arts and the dark paths their families seem to push them towards.
The theme of identity is often explored. She has to figure out who she is in relation to her father, the Black family, and the wizarding world at large. There's also the theme of friendship. In many fanfictions, she forms bonds with other characters that help her navigate through the difficulties. For example, she might befriend characters who knew her father or are also dealing with their own family issues. And power, both magical and political, can be a theme as the Blacks were a powerful family.
One common theme is family legacy. Since she is the daughter of Regulus Black, there's always the exploration of what it means to carry on the Black family name and all the baggage that comes with it, like the family's dark past and their pure - blood ideology.
One interesting plot could be her discovery of her father's past. Maybe she stumbles upon some old artifacts or memories that lead her to understand the sacrifices he made. For example, she might find his old Death Eater's mark and then try to piece together what it means for her family's history.