It was NC-17/Category III and I was slightly offended because I thought they rated it Cat III because it's a gay movie. Then one minute into the movie I was like, no, they definitely rated it right, since the first scene was two dudes actually having sex.
The first two thirds of the film is basically gay pr0n with a tiny bit of plot, mainly to let one of the two Japanese guys have sex with different white dudes. The last third of the movie was much more conventional and was quite sweet. And then I found out that the screenplay was written by the famous bara BDSM mangaka Gengoroh Tagame, so, duh. Oh, well, live and learn.