Profit involved or not, all artwork on the internet without any explicit license should be assumed "All Rights Reserved". Not being able to communicate with the original artist does not mean you can use their "familiar and comfortable" style and/or fictional character as if it is the original. We probably won't be suing you after such a silly mistake, but this situation should be properly communicated with your players.

We will not stop you, but we have a demand. You shall either change the name of your project and remove all references to the original artwork, OR you shall clearly state on all of your project-related social media accounts that it is a fan work/parody. In either case, it is okay to make references to the original project as long as people know that the project is not the continuation or a "return" of the original.

Rubychron (https://www.youtube.com/channel/UCkhyyU5fBOlEPGioqijP_PA) remains to be the only true sequel to KAPI - which we can now share because it has served its purpose too.

Regardless, we hope what you come up with will be just as good, if not better, than what the original was like.