Just remember that the dev does own rights to the game so he could claim any money you make on it if you go that route.
if we are talking about copyright the only thing the author "owns" is the story and in as far i know it will not go well in court due to the story is to similar to other works like in some counties you can pretty much changes only the names in the story and you "own" that story aka it counts as a "new" copyright so he can if the guy want pretty much use the same models and create a similar story with different names but in essence "same" story
when it comes to the models the author has only paid(that is if he has paid for them and not downloaded them from here for free) a license to use them not brought the copyright from the original creator
so it exist in the end very little that the author can do if someone ales do choose to make a similar game
as most the author can be mad/angry that someone is making the game with the "same" story but it is pretty much that
so i would not be worried on that front
but other then that i would still recommend that you changes more then the name in the story it exist more stuff you can do with the models then what is current being use in is story so i would try to add some new stuff into it if not even add some news ones(models)
because if the copyright laws was different then pretty much every "cosplayer" who sells stuff would lose money due to they would need to pay the original owner of the copyright (in the "cosplayer" case the character that they cosplay as)
even if they don't have a 100% the same look as the original copyright aka character
but then in the end i don't knows every copyright laws in the world
like take the game something unlimited here on f95zone would they not need to pay the original copyright holder for using character that they do not own and they also profits from it ? is that not against copyrights laws ? the only things that they "owns" would be the code that's if they made the codes themselves and did not use tools to make that games but wrote the codes themselves without using a mall(a set of premade stuff some sites is using malls so it take less time to make the site)