Her annoyance flared, but it was quickly replaced by that familiar, fluttering warmth she refused to show. She leaned in closer, watching his peaceful expression. Thinking he couldn't understand her, she switched to her native Russian, her voice dropping to a low, melodic murmur.

: The specific line you mentioned comes from a fan-made, adult-oriented animation posted by Totonito on X (formerly Twitter) and other adult platforms. It features voices intended to mimic the original characters in an explicit scenario. Official Anime Information

The juxtaposition of her cool, "ice queen" persona with her flustered, high-pitched Russian venting.

Fans often isolate these voice lines for their expressive and melodic nature.