In this paper, we demonstrate the trichotomic realization of voiced velars in Japanese, challenging the traditional plosive/nasal dichotomy of velar allophones, and examine the distribution of these allophones taking phonetic/phonological factors into account. We conducted the quantitative analysis based on some speech production experiments. The results show that voiced velars are more likely to realize as plosives in word-initial positions, as nasals in post-nasal positions, and as fricatives in sequential contexts; velars in word-initial positions can realize as fricatives; the decline of velarnasalization has been accelerated; following vowels and dialectal differences can affect the distribution.