Top o Nerae! GunBuster Vol.1 is based on the anime OVA series Gunbuster by Gainax. In the early 21th century humanity discovered a race of bug-like aliens while colonizing known space. The aliens steadily advance towards the Earth with the goal of eradicating it. To counter that, humans have developed giant mechas that ca be navigated by trained pilots. The story of the game follows closely the first chapter of the anime, focusing on the young pilot Noriko Takaya and her first steps towards the mastery of her dangerous profession.
The game has a Japanese-style adventure-like interface (with Look, Talk, and other verb commands leading to sub-menus), but plays more like a cross between an interactive movie (with animated scenes and voice-overs) and a visual novel, where choices of actions and responses play a dominant role. Every wrong action raises the heroine's "stress meter"; once it is full, the game is over.