The ground has a moving tunnel that soon encounters the roots. Shifting rocks try to tear them apart and make the person a way out.

His roots decline to be shredded until either whoever that is surfaces, or he gets bored and starts flying away.

What if the rocks really insistently try to make their way between roots to pull an opening through them?

Ugh. But there's space above them, right? The person can leave the ground if they want to?

Yes, he wants to look at them, that's the whole point.

Then a large muscular shirtless man shoots up like a bullet (or, well, the boulder he's standing on shoots up like a bullet) in the strange new parahuman's direction.

...Where he hits the roots' aboveground counterparts. "Peace, strange human." The language barrier is becoming irritating.

The strange human falls back on the ground and looks up at him, then asks something, gesticulating wildly at him and at the roots and at the ground and all around.

"I don't understand this language," he says demonstratively. He points at himself. "Tenno." He points at the stranger.

"...Jiwe."

Progress! He makes Jiwe a little berry bush (and an identical one outside the tree-cage, which he eats from) and points at or mimes various things, trying to get names. If Jiwe doesn't cooperate... Well, cross that bridge when you come to it.

Jiwe crosses his arms and doesn't eat.

"I don't want to hurt anyone, you know." Munch, munch. He shrugs and starts cantering away. On his way out he makes changes to Jiwe's tree-cage until it's sufficiently loosely built that he can probably dig his way out of it in an hour or so, then attempts to get someone around here, one of the magicless ones perhaps, to just talk to him already.

Well, most people seem to make a point of not getting in his way, and of course he doesn't speak their language so he doesn't know what-all they're saying whenever they see him.

This is getting quite annoying. If they already think he's evil, no harm in doing something less than polite. He picks one who seems less frightened than average and ties their feet to the ground with a tuber and repeats the I-don't-know-this-language-please-name-things process.

If she seemed less frightened than average before that, now she's significantly more frightened than she was before, and the words "hakuna" and "tafadhali" and "nakuomba" keep being repeated over and over.

Patience. Patience. Patience. PATIENCE. Can he get anything out of this by trying to appear calm and offering her food and miming at things in a strange language trying to get words?

She will eventually stop crying inconsolably if he waits long enough, and then meekly accept the food and never look him in the eyes and never say much more than two words.

Nope.

Tenno releases Jiwe from his treecage, re-imprisons him if he attacks, and tries the same process in another few towns. More of the same?

Not all towns have people with magic, but the ones who do pretty much all attack him on sight if they see him flying.