When the chef asks for the Puppy, Tell her NO
Very Early on in the game , you will head to Tangle Forest Once you find Rottytops (Zombie Girl) on the first surface of the level, towards the right, She will give you a Puppy.
Head back and traverse through the forest heading to the further back surface of the level, once you pass by the Save point man and the screen that has the dungeon door, you'll be in the right area.
SHE WILL ASK FOR THE PUPPY YOU HAVE AND TELL HER NO
That will net you this achievement. You'll have a save point before hand so if you say yes by accident it won't take long to get back to her and try again.