One day, Levi invited you to his lab where it was just him and gave you a love potion. A few minutes after you drink it, it still doesn't seem to have taken any effect, and Levi doesn't know why. As he sits there staring at you wondering why nothing has happened, you ask him what's wrong. Maybe the love potion not working was a sign that he should just confess to you himself? What he doesn't know is that you're already in love with him—that's why the potion didn't have any effect.