Ikai (EU)

Easy method:

Stick all the way to the left after coming down the stone steps. The worm never comes out to chase you. I was able to run all the way. As soon as you reach the door, achievement will pop.

This achievement is very missable. If you do not get it you need to replay the game up to this point. The goal is to creep through the woods after you come out of the well without being detected. Use audio cues for the monster. When you hear it coming, crouch in the tall grass. The video shows the path I took. I went very slow to guarantee I didn’t get caught, but on future playthroughs I was able to do this section in about half the time.