According to the series description of "Limited Lovers", the doctor, Okita Teppei, has a split personality.
Having read the whole manga, it is pretty obvious that this is not actually true.
I'm not sure how to phrase it better, but the current description is really quite misleading.
Perhaps "not only does Teppei already have a fiancée, but he also has a frighteningly ruthless side to his personality" or something similar.