He is hardly unarmed, and his establishment is well-protected. Whoever I might be, it is obvious that I cannot risk a frontal assault: not because I have no chance of overwhelming his defenses, but because it would lay bare my involvement.
So many of us have something to hide in Soul Society; I, Aizen Sousuke, do not rank high on his list. He must deduce that I cannot give up that advantage.
Another man might have been content with a stalemate. But he is a scientist.
Who I am does not matter. What matters is this: what would I do?