The Dead or Alive series is an interesting one; it's not so unusual for it to be a 3D fighting game, but many of the contestants are so-called scantily clad and buxom in proportion. The presence of the "Dead or Alive Extreme Beach Volleyball" spin-off underscores this.

The appeal to sexuality is obvious, but developer Team Ninja has been outspoken in the past about fans taking that sort of thing too far, in 2015, just before the release of "Dead or Alive 5 Last Round," DOA's first PC game, game director Yohei Shinbori urged PC gamers to "please play with morals and manners" and warned that "if things get out of hand, we will not release any more PC games in the series." Although he did not specifically cite nudity mods, the implication was clear.

(For the record, it took about 24 hours for the nude mod to appear).

Half a century has passed since then, and little seems to have changed: Koei Tecmo announced today that it will take legal action against the distributors of DVDs containing nude mod videos, including "Dead or Alive: Extreme Venus Vacation". The original statement is in Japanese, but Siliconera reports that despite the modification of the footage, the publisher considers it a case of copyright infringement and aims to file both criminal and civil charges as a result. This is Google's translation of Koei Tecmo's announcement, which warns that it will "continue to take strict action against copyright infringement."

Interestingly, while Dead or Alive 5 and Dead or Alive 6 are available on Steam in North America, Extreme Venus Vacation is a game in which players invite women to a private island to participate in a tournament to determine the most beautiful women: It is available on Steam, but only in Japan. Maybe they shouldn't have made a mod like that after all.

Update: Koei Tecmo has released an English statement confirming the legal action.

Unauthorized reproduction (including partial modification), distribution, or distribution of our copyrighted material is an infringement of the copyright holder's rights and is illegal.

We will take decisive action against such illegal activities. We will continue to take strict action against copyright infringement and strive to provide games that satisfy our fans.

While we do not deny derivative works,

we may take action in consideration of a) the discomfort felt by fans,

and b) the feelings of the developers.

Thank you, PCGamesN.