As Nora will unashamedly admit to, she cries when she doesn't get her Hogwarts letter on her 11th birthday. Ren has already has his but Nora has explained away him not getting a letter as Hogwarts wanting to send both of them a letter at the same time, because they're best friends. Ren doesn't say anything even though he knows nothing will happen, he doesn't believe in things as hard as Nora does.
They're having a sleepover so Nora convinces Ren to stay up late, waiting until midnight because they have to be wizards, they have to be.
Obviously, they aren't, magic isn't real and Ren pets Nora's hair as she cries, curled up the corner of his room closest to the closet. Then she laughs and Ren looks at her, startled. "I just realized this is like the fairies," she says, and Ren nods.
(/)
When they were nine, during summer vacation, Nora made a fairy house in her backyard by making a little fort out of sticks and leaning it against a tree. The next morning there were flowers in the house and her dad told her that this was because the fairies had stayed in the house during the night and the flowers were a thank you gift.
Later that day, she went out to water the flowers, and discovered to her horror that they were already wilting. Digging around in the fairy house she discovered that they were cut flowers with the cut off ends buried under a thin layer of dirt, not flowers grown magically overnight. Nora knew fairies would never do that, one of the biggest rules for fairies was never cut flowers because that was killing them.
So she ran to her papa and asked if he and dad had put the flowers there, not the fairies.
"Yeah," her papa said.
"Oh," Nora said. "Are there really fairies?" she asked, because even though she believed in stuff like magic and fairies she wasn't stupid either.
"I don't know," papa said.
(/)
She told Ren about this at their next playdate and he told her that he didn't believe in fairies, not really, he just pretended with Nora because it was fun.
Now, three years later with Harry Potter Ren admits again that he doesn't believe in magic, and never really has. And Nora nods, and says, "Doesn't make the book stupid."
"Nope." Ren says. He pokes Nora on the nose, and she giggles.