I think the basic point of the PV is Ayumi saying that there are sides to her that are hidden away from most people but the one she loves gets to see those hidden sides of her. You'll note her outfit where she's dressed in all black and she looks very much unlike herself, that outfit represents the side of her that very few people get to see. You'll also notice how throughout the PV everyone is messing up her eyes (Dark Ayumi's eyes are painted black) and their trying to rip up all her pictures, like destroy her. Then, the lyrics
"So
Even if no one in the world knows me
I wish you alone
To know me
Yes
Even if no one in the world knows us
We know each other
So well"
Suggest she's saying to the one she loves that no matter what happens to her or what she becomes he'll always know her and recognize her.
Just my two sense
