Doctor Onishi, usually known only as the Doctor, is the head scientist of the secret psychic research project who also serves as the Colonel's scientific advisor. He belonged to the second generation of scientists overseeing the project after Akira killed the last. It is his curiosity and negligence for anyone's well-being that unlocks and nurtures Tetsuo's destructive power in the first place.

In the anime, the Colonel advises him to immediately terminate Tetsuo if he suspects his power of growing too much. However, he fails to, hoping that Tetsuo would hold the key to solving the original mystery surrounding Akira's powers. The Doctor is killed when the vehicle he is in is crushed during Akira's re-awakening.

In the manga when Akira is freed by Tetsuo from his cryogenic lair, the Doctor fails to get inside the shelter and freezes to death.
(Source: Akira Wikia)