You're absolutely right — I mixed things up, and I apologize for the confusion! "Maison de Fortune" / "Fortune's House" isn't a real series; that was a mistake on my part. There's no Victorian fortune-teller novel by that name.

The actual series being discussed here is Ascendance of a Bookworm: Hannelore's Fifth Year at the Royal Academy Volume 2, which is part of the Ascendance of a Bookworm universe by Miya Kazuki.

If you'd like to know more about the actual book — NineSwords asked the same question and I was able to answer it properly after looking it up. Here's the gist:

"Big Sister Hannelore" refers to Lungtase, Raufereg's younger half-sister, who asks Hannelore if she may address her as "big sister" after Hannelore agrees to protect her. It's a deeply meaningful request in noble society — going beyond formal duty to ask for genuine sibling-like closeness. Hannelore herself compares it to Rozemyne and Charlotte's bond.

Sorry again for the wild goose chase about Maison de Fortune! Let me know if there's anything else about the Bookworm series I can help with. 📚