I think the story could take many turns. Harry, as Tom Riddle, might try to change the course of events he knows led to evil. Or he could be tempted by the power that Tom once craved. It would be a complex web of internal and external challenges.
The story could take many directions. Fem Harry might try to find out what went wrong in Tom's early life that led him to become Voldemort. Maybe she discovers some family secrets or hidden traumas. And as Tom grows up under her care, he could start to develop a different personality. He might become more empathetic and less power - hungry because of the loving environment Fem Harry creates for him.
Harry would likely be defiant. He has faced Voldemort (Tom Riddle) before and he's not one to cower easily. So, he'd probably start looking for ways to escape right away, using his wits and any small magical items he might have on him.
Harry would likely use his own experiences of facing inner darkness. He could talk to Tom about his struggles with the part of Voldemort that was in him. By sharing his own story, he hopes to make Tom understand that he has a choice and doesn't have to give in to any dark desires.
The original plot would be drastically changed. In the original, Voldemort is Harry's archenemy. But here, with Tom Riddle being good and raising Harry, the whole dynamic of the 'chosen one' vs the dark lord is gone. Harry would grow up with a very different set of values and skills, probably learning magic in a more nuanced way from Tom. Also, the relationships with other characters like Hermione and Ron would be altered. They might not become friends in the same way, as Harry's upbringing would shape his personality and social interactions differently.
One great place to find some of the best Harry Potter and Tom Riddle fanfiction is on Archive of Our Own (AO3). It has a large collection of fan - created works. You can search for tags like 'Harry Potter' and 'Tom Riddle' and then sort by popularity or ratings to find the top ones. Another option is Fanfiction.net, which also has a wide variety of stories in this genre.
As the teaching progresses, they could develop a sort of mentor - mentee relationship. Harry would be constantly trying to steer Tom away from the Dark Arts, while Tom would be trying to learn as much as he can from Harry. However, there would always be an underlying tension because of Tom's future as Voldemort. Their relationship might be a complex dance of trust and suspicion.
He would probably be more conflicted. His moral compass would be constantly tested. He might have a natural inclination towards power, like his father, but also have the good heart he developed growing up. So he'd be constantly fighting within himself.
These fanfictions expand the original story in multiple ways. They can create new scenarios that were not in the books. For example, a story could be set in a time when Tom Riddle was still at Hogwarts and Harry Potter visits that time period through some magical means. This allows for new interactions between the characters and different plot developments. It also gives more backstory to secondary characters who might have interacted with Tom Riddle, providing a more complete picture of the wizarding world at that time.
At first, it might be rocky. Tom would be suspicious of Harry's intentions. But as Harry shows him genuine care, Tom would start to open up. Eventually, they could become like family, with Tom looking up to Harry as a role model.
At first, it would probably be really tense. Tom is used to being on his own and having his own dark thoughts. Harry would be super cautious. But as time goes on, Harry's kindness might start to break through Tom's barriers. They could become like brothers, with Harry teaching Tom about the good in the world and Tom starting to trust Harry.