IF YOU REALLY CARE FOR A FLUID ACTION SERIES THEN DO WATCH IT(ONLY TO FORGET IT IN A FEW MONTHS).
The anime, despite having great visuals and audio, isn't something I would recommend someone to watch. 12 eps is really small stretch for any anime, and especially for sirious, it felt rather rushed.
The character designs were great and so were action scenes. However the storyline was really bland, and unexplained. The anime had a lot of scope, if it had more character developments, and more story to it.
Like seriously, I could imagine coming to re-watch this anime from time to time, had its storyline be as good as the lucid action scenes it offers.
So, to sum it up, was it a good watch? I would say, maybe.(I would have watched anything to waste my time). Would I re watch it, if I get the chance to do so? Nope.
As for anyone saying it was a "romance" anime, I don't know, haven't you watched proper romance animes ever?