Rakudai Kishi no Cavalry quick review:
The fan service... omg the fan service...
Ok, maybe I'm exaggerating a bit, but it does have some nicely done fan service, and it incorporates it rather well.

The story itself is the usual affair. The usual sword fights with magic mixed in, with a protagonist that supposedly lacks natural talent for the magic part, but with hard work, against all odds, he rises to the top.

Nothing fancy or particularly noteworthy, so it doesn't get more than 7/10 from me, but it is still good enough, that if you're looking for a short 12 episode anime, it gets a definitive recommendation.