i think that its about her and her friend....'2 little kids playing' and that utada probably died and now watches over her friend, following her and everything....then the bit where she pushes her friend out of the way she saves her and then she's finshed with wat she wanted to do which was look after her friend and the 'hit by car and dying' symbolized her actually being gone now that her job was done. if u watch, no1 sees utada until the end only her friend does, thats y every 1 walks around her and no 1 sees her when she dies