I know what the butterfly dream is... it's a theme used in modern piano arrangements.

[She pouts at him, but lets him continue with his explanation as they walk, adjusting her grip on the books every now and then to make them easier to carry. A familiar is an extension of the mage themselves...? It kind of reminds her of how Gundam talked about his hamsters, except she's pretty sure that back home, they were just normal hamsters.

She hums in understanding, though, nodding every so often.]

I think I get it... Well, even if Erika-san were a butterfly dreaming of being a human, I'd still be her friend!