[Doctor]

Names aren't always so 'pretty,' true.

But Sephiroth WAS an experiment, and it seems weird that he would have a last name at all. His first name alone was probably just his experiment name, and wasn't even given to him out of affection, or anything like that. So, you could say that 'Hojo' is his last name because Hojo is his father, but it isn't OFFICIALLY his last name. At least it shouldn't be. But this is how I gather it, so...