The past emperor and the present emperor have nothing to do with each other , right? Is the present one the reincarnation or the descendant of the past one?
Both of them are reincarnating with theirselves. The past keeps repeating itself with the emperor abusing the slave, etc. Also the reason why the slave hates the emperor in the present is because he remembers what happens in their past timelines. Although it seem like the events in this timeline is getting different from the previous ones like the emperor being more considerate, understanding and uhm less tyrannical so you could say that the past and present emperor are kinda not the same.
Anyways , their bodies.... Look so weird