Gunbuster, known in Japan as , is a six-episode anime OVA series created by Gainax in 1988. It was the directorial debut of Hideaki Anno, best known as the director of Neon Genesis Evangelion. The title is a combination of the titles of classic tennis anime Aim for the Ace! and hit action drama film Top Gun, whose plot inspired Gunbusters. To celebrate Gainax's 20th anniversary in 2004, an official sequel to Gunbuster, Diebuster (or Gunbuster 2), was released as an OVA. The sequel features new characters and mecha, but retains the format and many of the concepts of the original series.