no kuchi ni naru
have a mouth (for certain food)
to feel emotionally ready/eager to eat something and don’t feel like the other foods at the moment
It often suggests you have some specific reasons why you’re craving the food. For instance, you’d have “a mouth for ramen” after watching a TV show that features famous ramen restaurants; viewing a series of mouth-watering ramen pics; or having a long discussion with your friends about your favourite ramen restaurants.
What? The yakiniku restaurant you were just talking about is not open today? Coz I’ve got ready to eat yakiniku already, let’s find another yakiniku restaurant!