Hello Degenpink. For me I went to the love and caring path since the start of the updated game so what I did is just basically do normal things basically by just either patting her head, giving food, sleeping with her or just following what the pc says that leads into a scene etc. Then after doing that I just bought the potion between late night. Go to work , then I went home between 18:00 or 19:00 evening time then the scene starts. That’s how i got it
The potion will only work in the new update version of the game. I tried that one time with the old demo version of the game and it didn’t work so I restarted from zero to go on and finish the game. Hope this helps you.