Hayabusa

From Storm in Heaven:

They are coming, and Kazuki must find a way to harness the power of the Falcon before They come to kill him. But becoming the Official Falcon is no easy task, and even if he succeeds in awakening the Falcon's power, there are rules he must follow in order to capture Them. If Kazuki's conscience cannot maintain control over the Falcon's power, he risks falling to Their level, and facing an unknown destiny. His aspirations are no game, for failure means death…or worse.