This Paper discusses the issues related to the grammatical features and functions of the o as showing a Period and naka-o as showing a situation. In the usage of case particle o, these forms of o were considered a sort of the usage as showing a move and path in precedent studies. However, there are grammatical deferences between the period o, the situation o and the path o. The first point is that we should discuss that the grammatical features of the period o, the situation naka-o are different from the path o. In order to know that, it is necessary to analyze the indispensability of noun phrase revolving around a verb in a sentence. Moreover, it is also necessary to analyze that there are the differences of movement between the situation o and the path o. In conclusion, it is clear that the period o is parted in the period o① of the indispensable case and the period o② of the secondary case, i.e. the period o② has a different grammatical function with the path o of the indispensable case. Situation naka-o is also parted in the spatial naka-o and the temporal naka-o. The spatial naka-o has a same movement with the path o, but the spatial naka-o is the secondary case. The temporal naka-o has a temporal movement and the grammatical function of situation component.