[video]
Hikaru Hitachiin has experienced this before. When he left the dome he came back remembering things he didn't know about before and his hair was dyed again! Before he left the dome he'd been from a time before that happened so when he left it seemed like time at home had moved forward for him again. But even though seemed to have gone home he didn't remember ever leaving the prison.
And some times there are people who leave and don't have any memories of being here at all and only of being at home... [He's talking quickly when he's explaining this and at the end he just sort of trails off. It makes him nervous when he thinks of his friends leaving and how little he actually knows about what happened to them.]