Complex sentence: Tetsuo goes missing in the explosion, and Kaneda and Kei come across Akira outside of the base and--vaguely aware of who he is--take him back into Neo-Tokyo.
Split into simpler sentences: Tetsuo goes missing in the explosion, and Kaneda and Kei come across Akira outside of the base. Vaguely aware of who he is, they take him back into Neo-Tokyo.