MC is very old and approaching the end of his life. For some reason though, his old age ailments start to slowly go away. He starts to feel better, more spry, has more energy. This continues very slowly for awhile with the MC only realizing it is happening when he compares himself to others the same age and they seem to be 20 years older. He then mentally reviews his health over the last months/years and hypothesizes that he is slowly regressing in age. This causes him initial elation but then comes fear and confusion because he doesn't know what caused it, whether the regression was temporary or permanent, how long he will continue to regress for, is there any way to stop the regression at a specific point, the effect his becoming younger will have on friends/family/public/government,etc.
