Yes, Giulia. She's the main character, and Hugh is secondary. Although that doesn't mean that you couldn't write a book where their roles as main character and secondary character were reversed, still it seems to me that the series is about Giulia and writing an adventure about her in which he doesn't appear sounds like it would be perfectly satisfying to readers. I mean, some readers might miss him, of course. Readers do get attached to secondary characters or even sometimes quite minor ones. But the real question is, would it be satisfying to you to write a story that is Giulia's adventure alone. You're the writer and if that is where your inspiration takes you ....