A native speaker of any language is one who uses that langauge as his first language... if you are japanese born and raised there you will be a native japanese speaker and fully conversant and fluent onthat language.. I am british a native of the british isles and a native English speaker... I know a woman who is from hong kong who is Chinese and she can speak English having lived in England for 34 years but still makes chinglish grammar mistakes when she speaks and writes.