Summary: Waking up in a jail cell that's not the same one as he was in, Eren is in someplace called the Velvet Room. There was a strange man with a bald head, long-pointed ears, and a nose. Saying that he's on the path of rehabilitation.
Later. He discovers a strange device no one has ever seen before, and his titan powers are completely gone. But now Eren found himself in another reality and gains new powers. Powers of a Persona.
Sorry, that's all I got so far. But just to let you know of which persona universe Eren is in, it's the Persona 5 universe.