For a significant character to leave a story, do you think they always have to be killed off?

that does happen occasionally, but generally they always reappaear. um... but that would be cool to see whether or not it's not usually seen in books. i always get excited when i find out/think of something that hasn't been done before, so props to you :-D this character would be perfectly free to leave once he was free. maybe have kinda scene where they watch him walk away or even something from his POV about him being super ecstatic about being free and having the whole world in front of him. however, he shouldn't be entirely gone. otherwise, it would seem like you just wanted to change the name of the character with his personality when you put in the new guy. instead make sure to say something about how they miss him or the new person remind them of the old person throughout and possibly wondering what he's up to, but only in idle moments, or just when the reader might risk forgetting about the old charcter/wondering what happened to him, or maybe even just times when the new character says something or does something extremely similar to the old character. did that help? also, i'd be happy to edit it for you once you're done (i'm interested in reading the story hehe :-) )