Is Queen's Blade: Rebellion Specials hentai?
No
Rated R+ (Mild Nudity) on MyAnimeList and not tagged as Hentai.

Special · 2012 · 6 episodes · R+ - Mild Nudity
Ecchi
Specials included in the Blu-ray/DVD volumes. Each special will be about a different character.
View on MyAnimeListShare
Check another title