You'll get this after the nightmare scene at the very beginning. I think it's a Junji Itô reference.

At some point in the game, you'll hear a knocking sound coming from your door. The achievement will unlock after you answer the door.

When you go on a breakfast date with Gemma, she'll ask you to name Mr. Kovac's cat.

Moon River is the main theme of the movie "Breakfast at Tiffany's", you need to name the cat after the famous cat actor that played in this very movie.
If you are too lazy to google it, you have to name him Orangey.

You need to name the cat after the title of a Haruki Murakami novel.
Again, if you don't feel like googling it, you have to name him Kafka.

Note : The game will autosave before the final choice, there is no need to restart the whole game to get the other endings.

This is the good ending. At the end of the game, you will have to chose between going to the clinic and going to the cemetery. Go to the cemetery, then choose to stay when asked. You'll receive the achievement after a short while.

This is the normal ending. When you are asked where to go, choose to go to the clinic.
You can have it by also going to the cemetary, then choose to go back to the clinic, which will give you the Box achievement. Then when talking to Gemma later, select "Let her in" then choose the "Letter" dialog option.

This is required to get the two bad endings. Select the "cemetery" option, then select "go back to the clinic".

This is the bad ending. After Box, Let Gemma in and don't tell her about the letter.

This is the worst ending. After Box, select "Find an excuse" then go to your bed.