Prologue

The game suggests you play this mission twice: once to learn and a second time to aim for an A rank. You can't get the best rank on your first playthrough because you need to complete it in 1 phase, which the game's tutorial pacing doesn't allow. So, after your first run, save and then reload the mission to try for the A rank.

To get an A rank, pick either Alicia or Welkin (they're your best options here). Use your first Command Point (CP) to move them forward. Your objective is to get close to the first enemy, go over or around the bunker, and shoot them in the back of the head. Don't be afraid to get right up next to them; they won't notice you until you're practically on top of them and won't attack unless you're spotted. If you're having trouble lining up the shot, you can even wait for them to turn around, though hitting the back of the head is ideal.

Use your second CP with the same unit. Move up to the second enemy and shoot them point-blank in the face. You can take a hit or two, so don't worry too much about getting shot.

Continue moving towards the third enemy. Use your third CP to approach them and shoot them point-blank in the face as well. It's pretty straightforward!