Fanservice (サービスカット) is content in an anime or other work that is meant to please the fans. This is usually achieved using Boobs.
Since Gunbuster and Diebuster are OVAs, they can get away with showing boobs uncensored, thereby increasing their power.
The concept of Topless is surprisingly unrelated to fanservice, at least when Nono isn't getting the two confused.
- The Gunbuster Episode 2 bath scene. (Pictured)
- The Diebuster Episode 2 bath scene.
- Nono ripping off her shirt for no reason in Episode 1 of Diebuster.
- Gunbuster's use of Gainaxing.