And the correct answer is…
You should slurp your noodles on each mouthful, not just the last.
As opposed to the U.S. where slurping any food will result in glares and chastisement, slurping noodles such as ramen, udon, or soba is perfectly acceptable behavior.
Some will say that this is to show your appreciation for the good food- that it was so good, you had to eat it while it was still too hot.
Additionally, slurping draws air over the noodles, adding to your perception of the taste of your food.
Happy Slurping!
Courtesy of Ivan Ramen/Daniel Krieger