At his shield and spear's most decisive moment, Bai Wu had only attacked from behind once before, and that was the direct cause of that person's death; if one person must die without doubt at this time, it is his first number one.
Bai Wu's most obvious front-back logic with his shield and spear had become the initial round of advancement, from number nine to number one, in short.
Bai Wu had also done his utmost; Lin Rouwu could not survive.
The fourth token shield was his Forbidden Word Card, simultaneously with Lin Rouwu's.
The third token shield of Lin Rouwu was his crafted lie to Lin Rouwu; the second token shield of Lin Rouwu was her own Number One Self-Destruct; the first token shield of Lin Rouwu was his own self-destruct.
He had given the four token shields to Lin Rouwu. Bai Wu needed to protect Lin Rouwu, this being one of his prime objectives.