Damn, that took some zooming, multi-radical search and guessing to decipher what's written to the left of the last bubble. Turned out it was the same thing Yuuki said >_<
@HYBRID_BEING@SveNo It's English-spoken in the original version too because of Yuuki's mixed origins
https://sai-zen-sen.jp/comics/twi4/otomedanshi/0487.html
Ah, that explains it. Thank you!
Edit: Come to think of it, Yuuki did speak english in at least one earlier chapter but then the translator graciously pointed it out in a footnote: https://mangadex.org/chapter/529670/1