In most games getting the highest score, or running through a stage and getting the best record can be very difficult. However, by practicing a stage or a scene over and over will usually help out in getting that achievement. Aragami is no different, and will call for precise movement when going about a mission when trying to achieve the mighty S Rank.
One move (among other essential moves) that will help in several cases is the Shadow Leap skill. You can use the Shadow Leap skill by staying in shadows and filling your Shadow Essence meter up, which will grant you the ability to teleport.
With all of that said, six stages completed perfectly can be seen below. These videos come in by YouTuber Centerstrain01, which if you are stuck on any of the stages, a list on the side shows each of the six stages and how to beat them.
If you are not in shadows and stick around in brightly lit areas your Shadow Essence meter will drain, this will obviously hinder your movement since you won’t be able to use your Shadow Leap to get around enemies and places faster.
The key to getting an S Rank is to avoid as many enemies and light sources as possible. Carefully walking and planning your next moves are more than needed if you are after the highest score.
I should note that some Alerts Raised can be on the end chart, but not too many. Other things you should consider while doing a mission is finding all the collectibles to ensure an S Rank at the end of a chapter.