NOTE: This is the rating for the whole series (I read it online, and a while ago as well, so I don't know the separate volumes)
This was just a really great, hot, action-y with a shitload of sexual tension and a gay-for-you theme going on. It was probably one of the first yaoi mangas I've read, yet remains one of my favourite.
Have fun blushing at the sexiness of this.
Note: They actually work up to the sex, it's not the kind wham-bam thank you for the orgasm with that quick and dirty sex scene. It'll make you squirm (in a good way).