As a rule, I don't try to answer questions about languages I am not fluent in, however... I have noticed that Koreans tend to not start making the "N" sound prior to the moment they begin to move the tongue off of the roof of the mouth, which results in the "D" like sound. Similarly, when an "M" sound is at the beginning of a word, it sometimes sounds like a "B" due to the beginning of the sound and the lips parting coinciding.

네 = yes or 예(ye)

네

Ne 네 but the korean people pronounce it De !