As Belial walks off, Rhys approaches Chiaki. Because she has the virtual pet, he pieces together that she's the Unbound, and he apologizes for taking it. While Rhys knows of the device, he doesn't know it as UsaMaMa-chan, but as Bunnie Buddie.

This all leads to some confusion for Chiaki (and likely, for us). Chiaki and Rhys are from the same world, but they're from different parts of it, that would speak different languages. If they encountered each other in our world, Chiaki would be speaking Japanese and Rhys would be speaking English, and they probably wouldn't understand each other much, if at all. But in this other world they've come to, they're literally having a full conversation. This all goes way back to the beginning of the story when Chiaki questioned how she could converse with Redge and Nara.
https://tapas.io/episode/2723503

Many have been suspecting there's some "translation magic" in effect, allowing her to continue to speak Japanese and have words translated in real time to be understood by everyone around her. This has led to some interesting questions. How does Chiaki hear pronouns? How does everyone else hear honorifics? What did "itadakimasu" sound like?
https://tapas.io/episode/2943324

It's both simpler and more complicated. Chiaki speaks the language here since she arrived (even if she can't read it). Everyone understands her, and she understands them, because they're all literally speaking the same language. She can still speak/read/write Japanese - Aphaian hasn't replaced it - but this new language sounds natural to her because it actually comes naturally to her now.

It's okay if it's still kinda confusing, because frankly, it is. I mean, how and why is this even happening?

And after that bombshell, Rhys drops another one with, "This is just your life now." But can that really be? I mean, yeah, she speaks the language and now she casts the magic, but...

...but she'll go home eventually, right?

Right!?