Obviously, Harry Potter himself. Then there would be the four founders: Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw, and Helga Hufflepuff. They could be present in some form, either as ghosts or through memories guiding Harry. Dumbledore might also still play a role, perhaps as a sort of mediator between the modern world and the founders' teachings that Harry is receiving.
Well, in this type of fanfiction, Harry's parents, James and Lily, could still be important. Their memories or the things they left behind could interact with the founders' influence on Harry. And of course, the villains like Voldemort would be there. Harry's upbringing by the founders would give him a different approach to fighting Voldemort. Additionally, the Hogwarts professors would be involved, as they would notice the very different Harry who has been raised with the founders' ways.
There are many possible characters. Harry's friends, like Ron and Hermione, would be involved as they react to this new Harry. The house elves might also be part of the story, as the founders had different views on house elves. For example, if Harry was influenced by Helga Hufflepuff, he might have a closer relationship with the house elves and try to improve their situation. And there could be other magical creatures that the founders had a connection with, such as the centaurs or the giants, which could come into play in the story.
Chapter 906, "Big Brother, are you jealous?", is the clearest early answer because it turns Jiang Bufan's situation into a concrete plot event. The chapter turns that into something concrete by moving from A few people were somewhat surprised.
Chapter 28 is the strongest chapter-level answer because it starts from The next evening, Jiang Yan drove home seething with rage. and follows through on Lili then kicked his knee hard..
A practical answer is Chapter 37, because it turns the idea into a concrete scene. The chapter opens with The barrage was suddenly filled with hahas, but the two guests present..., adds pressure through The moment her gaze landed on her, she couldn't help but pause., and ends on I look forward to.
The best chapter pointer here is Chapter 36, "The Coldest Variety Show Opening in History". It opens with But soon, people began to question the authenticity of Jiang Li's bare... and closes on After swallowing the food in his mouth, he hurriedly took his megaphone....
Chapter 17 is the strongest chapter-level answer because it starts from Jiang Li glanced at Jiang Shixu, who was tense and anxious behind her, and... and follows through on I've been a mother for more than ten years but never tasted anything made....
The best chapter pointer here is Chapter 31, "Master, I've been having some bad luck lately!". It opens with Before Shen Lan had reached the backyard, she already heard the sounds of... and closes on After staying in the study and reading for another day, she finally....
Chapter 797, "Bu Fan and Bu Chen", is the clearest early answer because it turns Jiang Bufan's situation into a concrete plot event. The chapter gives readers a real answer by opening on The night grew deeper, and while waiting for news, Jiang Li dragged...
If you want the clearest chapter reference, go to Chapter 16. Early on, Just as the words fell, Jiang Shixu swiftly cast his eyes downward.; later, the chapter leans on His eyelashes were very long; when they fell, they could cast a small....
Chapter 927, "Jiang Li: Deceased, Do Not Disturb", is the clearest early answer because it turns Doomsday Beehive's situation into a concrete plot event. Early on, Doomsday Beehive" made over fifty million in box office sales within....
The best chapter pointer here is Chapter 60, "The Human Oil King". It opens with What's with Jiang Yan, treating his own sister Jiang Li like this?" "He... and closes on And in traditional characters?" "What else?.