Glad you liked the Rin feature!
About Yoru: yes, it’s intentional that she only needs 3 vodkas the first time to unlock the scene. After that, just 1 vodka works to trigger the unconscious version again, so you don’t have to waste money. And yes, for now she only has the unconscious scene!
As for Sakura, try giving vodka to Yoru first, then go back to Sakura's office. 😏
And great idea on the vigor potion! I’ll definitely think on it 💡