The Ainu language is one of the peripheral languages indispensable to the genealogical and comparative study of the Korean/Japanese languages. It is linguistically far from being genealogical with the Korean and Japanese languages, and is regarded as an isolated language. The main reason is the incorporating character of the Ainu language. But the Ainu language shares similar structures with the Korean and Japanese languages, and it is believed that in ancient times the Ainu language, in many respects, shared in the same group of Proto North East Asia languages. The formal characteristics of Gender, Number and Case in the noun of the Ainu language is completely the same yet the Ainu language is different from other languages for its peculiar personal form. But in the changing process of this personal form, the personal affix appears with the unjoined form, and it is believed that the Korean/Japanese language already experienced this changing process. Thus we have reason to believe one hindrance in comparative study of the Ainu and Korean/Japanese language is removed. Similar roots can be abstracted by formal analysis of the nouns of the Ainu language which is apparently different from the Korean/Japanese language. Such abstraction is possible in the words of the same field. Moreover in the respect that it maintains even the peculiar /h/ sound intervention phenomenon, it seems that these forms are not accidental similarity but the more original things. It is such things that show us the possibility of comparative study with the Korean/Japanese language.