[Allyship is necessary - vital - in a place like this; perhaps unfairly, Armin still considers Kate a child. Even if he knew her age, he wouldn't want her to have to fight. He doesn't want anyone to have to fight, but especially not children. He's so tired of watching children being thrown into war.

[She could be a liar, or a demon, or some other terrible trick of this place, but there's no way he'd be able to abandon her now.

[He gives her a steady smile - certain, though he isn't - and nods.]

Then we will. I promise you, Kate. [Can he keep it? Doesn't matter. He makes promises all the time that he can't necessarily honor. Oh well.]

For now...

This seems like a safe place to stay. [He doesn't want her running off on her own, but he can't exactly tell her that.] A home base, maybe.

If you'd like to stay here, I'll come by too. [To check on her.] We'll all need a place to sleep eventually.

How does that suit you?