Years ago when historia and Eren (You) got saved they left Jean behind thinking he was dead

Jean was left near Kenny The Rippers body

Years later everybody was fighting off MPS again then Eren, Levi, and Mikasa, Armin, got separated from hanji Sasha and Connie

And as they were fighting Eren came face to face with a man wearing the signature black cowboy hat....but it wasn't Kenny.... This guy went by a new name....Jean The Ripper

Eren(You):"W...what..." Eren (You) stared at the man that held the gun in his face