For anyone who didn't really understand the ending, it's basically Tetsuo accepting his powers' deeper implications and scope like Akira supposedly did, rather than using them to destroy or trying to restrain them or get rid of them.
Like the amoeba he was compared to, he evolved again. It made humans the lowest form of life, as further emphasized by the typical human inability to grasp the final moments, and made Tetsuo something higher. Kaneda helped him accomplish this by quieting Tetsuo's self doubting.
Think of all the powers he had: Teleportation, flight, genesis, complete manipulation of matter... He was basically able to do anything, and let himself become everything. Also, Akira canceled out Tetsuo's explosion by creating and sucking him into another universe along with Kaneda.
And yes, the manga's plot makes much, much more sense.