Akira is a young child recruited by the government for their secret parapsychology project, and was assigned the number 28. The project forced Akira to develop powerful psychic abilities. During this time he met and befriended other children involved with the project, notably Kiyoko, Masaru, and Takashi (later known collectively as the Espers.)
Akira's powers grew rapidly, and grew beyond his control. On July 16th, 1988 they destroyed the original Tokyo in what appeared to the rest of the world as a nuclear detonation, starting off a chain of events which quickly led to World War III. Akira was retrieved by the scientists, and was dissected to discover the cause of his sudden psychic growth. The scientists were unable to solve this problem, and the remains were sealed in cannisters and cryogenically frozen underground, sealed away as to prevent any chance of problems in the future.
The existence of Akira, and other remnants of the project become a contentious issue within the upper echelons of Japanese politicians. While the project is considered one of the highest of state secrets, periodic leaks have lead to Akira becoming a messianic figure among some cults in Neo-Tokyo. Minister Nezu, seeing this as an opportunity to gain further political power, manipulates a dissident group, known as the Resistance, to free Akira, to further his own ends.
Tetsuo Shima, upon hearing of the existence of Akira, rampages through Neo-Tokyo in a quest to find him, and learn how to increase his power. Tetsuo finds and destroys Akira's container, and ultimately discovers the truth. Later, when Tetsuo's powers grow beyond his control, causing his body to swell into a grotesque mass, Akira is summoned by the Espers. He appears not as a ordinary human being, but as a spirit-like form who has transcended the limitations of a human body. Akira utilises the power with which he destroyed Tokyo to absorb Tetsuo, and contain him in a new universe.
Tetsuo's friend Shotaro Kaneda was unwittingly caught in the explosion and he experiences both Akira, and Tetsuo's memories before being transported back to Neo-Tokyo by the Espers.
Akira is a young child, therefore he has a personality akin to a small child his age. He gets along well with the Espers as they were fellow government test subjects, and is shown to have delight in Masaru's display of telekinetic powers. He is willing to help his friends in battling a mutated Tetsuo, even if it'll destroy Neo-Tokyo in the process.
Unlike in the adaptation film, where Akira is a supporting character, he is a main character in the manga. Akira was a child test subject, designated number 28, who was part of a secret government parapsychology project where its members tried to research the availability of psychic powers in humans. It went horribly wrong when Akira's powers went out of control and utterly destroyed the original Tokyo in a destructive explosion - out of all the child test subjects who were in the project, only Akira and the Espers survived. While the Espers still lived, albeit in aged states, Akira was imprisoned in a cryogenic chamber and kept underground to avoid further disaster. Several years later, Akira was made part of Kiyoko's prophecy that he will destroy Neo-Tokyo due to Tetsuo's involvement. As predicted, Tetsuo unearths and releases Akira from his cryogenic imprisonment with the intent of using him, but when Akira is exposed to Takashi's death from an assassin's bullet meant for him, he is traumatized psychically and destroys Neo-Tokyo, killing millions save for a small group people the remaining Espers saved in their efforts. He is later taken in by the Great Tokyo Empire where he is made Emperor and worshipped as a 'god' by its followers for his "miracles", but in reality his autistic-like personality made him more of a figurehead. Akira is later the subject of a failed assassination attempt by a Japanese soldier, George Yamada, and formed a psychic link with Tetsuo, which allowed both boys to not only share thoughts but also pain. During the climatic battle, Akira is shot by Ryu, a former terrorist, to stop him from destroying Earth with Tetsuo, but ends up "restoring" his former personality. With the help of the Espers and a resurrected Takashi, Akira is able to use his powers to cancel out Tetsuo's explosion and absorb him.
Akira, unlike the movie, is figuratively an empty shell of his former self; his psychic powers have increased to the point where it has destroyed his personality. He almost never speaks himself or reacts to external stimuli, making him vulnerable to the manipulations of other characters, who either seek to destroy him or take control of his abilities, mainly Tetsuo.
Akira has a variety of psychic powers due to being a test subject for a series of secret government ESP experiments in the 1980s, among them are telekinesis, telepathy, and teleportation. All of them have developed their potential to where they became almost god-like - even a simple act of using them is capable of causing massive destruction on a large scale. Akira, presumably, had lost control over his powers once, in both the film and the manga, destroying the original and Neo-Tokyo accidentally, but in the end, he seemingly gained control over them.