This guide contain alot of tips that can help you tu unlock this hidden achievement.
Be Divorced From Achievement Guide
In the hide-and-seek section, go to the girl’s bedroom, and use the chair in the bedroom to face the mirror in the toilet to find the hidden door.
In the white forest, don’t choose to sacrifice yourself or contact purple men in the tall building, and trigger Detaching ending to get it
Also use the dagger on the creature entangled with a tree in the area to the left (saying “So… painful…” when you first interact with it).
Go back to get the purple slate, and place it with the others on the center of the zoomed out area.
Continue the game like normal and you should get it.