Btooom!: Bakusatsu Digest
Genres: Action
Type: ONA, Episodes: 2
Aired: Nov 16, 2012 to Dec 19, 2012
Studio: Madhouse
Source: Manga
Rating: R - 17+ (violence & profanity)
Synopsis:
Originally streamed on the official Youtube and NicoNico channels and later included on BD/DVD Vol.5.

(Source: AniDB)