Khong means "no" in Vietnamese. The original VN lyrics(more)

mean: No! No! I don't love you anymore(repeat). Because our love has been betrayed. All promises have been broken. We can only find love in next life! etc... The Chinese translation of "Khong" also mean 空 in VN served as good in the Chinese song.

I enjoy your singing in Japanese and you have a wonderful voice. Thanks!