Basically, when a person gets corrupted, the corruption takes over both their body and mind, but the thing is, that corruption never lived through all of these memories, so it creates false memories(not by command, it happens on its own) and so the body and mind follows those memories. The corruption acts like the host, with ofcourse different settings.
Sometimes, the corruption CAN gain feelings towards somebody else, but the host cannot, as they and the corruption, are 2 different entities.
Except for Phantom, as he was born from the corruption itself, both he and the corruption have the same memories, except that the corruption hates his boyfriend, alot.