This mod replaces emil's head item, so make sure to equip it !
there are two items: emil's head and emil's mask (emil's head is the item you want).\
1. Download the mod
2. Go to your game's directory \NieR - Automata\data\et (if you don't know your game's directory, you can right click on the icon, then click "open file location)
3. Unzip the folder in here (create an et folder if you don't have one)
4. Play the game (equip Emil's head item)