Hi there,
In the typical game, you get it by taking the 'Elixir of True Sight' (Or something like that, I can't remember the exact name). You can get it by having: 1) A high botany skill (something like 50 or 75), 2) Hacking the recipe from Fiona's laptop, 3) Cultivating rare plants in the greenhouse after you have a high botany skill.
After that you can craft the potion in the greenhouse. It'll only change headshots though. The other images (like with Fiona's revenge path, that have dual IRL + anime pairs) are automatically visible even if you don't have the potion.