Board Thread:Manga/@comment-27441457-20171006223515/@comment-1327106-20171022230718

We don't know how/when Eren arrived yet.

We do know that he was walking along with other injured Eldian soldiers so we can guess that he snuck into the ghetto by pretending to be one of them. That's how he got to the hospital, because he was among the injured.

Zeke, Reiner, and Pieck presumably went back via boat while everyone on Paradis was busy cleaning out the remainder of the Titans.