Unintentionally funny?
First off, the bad guy of the movie, portrayed brilliantly by Noriaki Kamata, should have had way more screentime. His performance was hilarious.
The whole film really should have been a black comedy, as it already raises a few unintentional lolz throughout. But instead it takes itself way to seriously and goes for cheaply done gore shocks and a very clumsy revenge plot. The 'master' surgeon who trains a prostitute to fight etc, then clumsily inserts a large handgun inside her, is laughably done, and doesn't make sense. So many other ways of smuggling a gun without half killing someone in the process. Also, the tubby asian chick doesn't lose an ounce of weight during this supposedly rigorous training.
Anyways, watch it for some laughs and Noriaki Kamata's performance, if nothing else.