"Devil? What have they been responsible for?" He's wary of them already, even without an answer. The fact that Devil is mentioned alongside Tower, and as wanting bloodshed among the Travelers...

But that knowledge also makes Eren more relaxed with his current company. "I will never turn against my friends. But as long as you don't expect me to, maybe we can work together to stop Devil and Tower from trying to do shit like that. Besides, if all you want from me is that I keep moving, I don't exactly have a choice." To stop moving is to stop fighting. To stop fighting is to wish for death. He'd been there, once - but never here, never as a Traveler. So as frustrating as it is to continue doing something that a Trump wants him to, it's not something he can simply stop doing.