This paper investigates tonal phenomena in Nagasaki Japanese (NJ), especially in loanwords, and argues that the pitch accent system of NJ is sensitive to the position of pitch fall rather than the presence vs. absence of pitch fall. There are two types of tonal patterns that may occur in an NJ word: Type A tone (a fall pitch pattern) and Type B tone (a non-fall pitch pattern). Previous studies on ongoing tonal changes in Kagoshima Japanese (KJ), which has a tonal system similar to that of NJ, revealed that accented words in Tokyo Japanese (TJ) are realized as Type A tones and unaccented words in TJ are realized as Type B tones in KJ. In contrast, a loanword in NJ is realized as a Type A tone if the loanword is accented on either of the first two morae in TJ; otherwise the loanword is realized as a Type B tone in NJ. This paper proposes that both NJ and KJ speakers have TJ forms as input, but only NJ speakers delete an accent on the third or later mora during the adaptation process. The proposal accounts for the tonal neutralization of compounds in NJ, which occurs when the first member contains three or more morae.