貞本義行
is a Japanese manga series written and illustrated by Yoshiyuki Sadamoto and published by Kadokawa Shoten. It began in "Shōnen Ace" in December 1994 and ended in June 2013. It consists of 14 volumes, each composed of several "stages" or chapters. It was initially released before the TV series of the same name by Gainax and Tatsunoko Production and was originally intended as a companion adaptation to that of the TV series.