Aragami

Before you can earn this trophy, you'll first need to unlock the 'Shinen' Shadow Technique. Once you've unlocked this, locate a group of at least three guards and place a Shinen marker nearby. Now, attract the guards' attention towards where you've placed the marker (the noise-making charms that you'll collect in chapter 3 are ideal for this), and once all three are in range of your Shinen (look for the indicator that appears above them), trigger it with a second press of to 'swallow' all three together - and earn this trophy.

Here's a video guide, courtesy of Trophy Germany: