Aragami

A guard's 'caution' mode is triggered when their awareness indicator fills fully yellow and a question mark appears above them. They'll then approach the location where they saw/heard you and investigate - but if they find nothing, they'll return to their post after a few seconds. To earn this trophy, you'll need to allow a guard to enter their 'caution' state and return to their post twice. Now, if you trigger their 'caution' state for a third time, you'll earn this trophy.

During chapter 3, you'll collect a pair of chimes that you can use to attract guards' attention using , which I'd recommend as perfect for earning this trophy with minimal risk of being discovered.

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