It is well known that the Japanese language possesses a large set of sentence-final particles which typically occur in conversations. They are signals of the speaker's various sentiments. Especially it is difficult for foreign students to use yo, for the hearer feels impoliteness on the expression of the speaker used yo. When the speaker uses yo, he/she has a sort of conviction on the information he/she conveys. So yo expresses an advantage of the speaker over the information. As\na result, the speaker adds impoliteness to what he/she wants to say, putting yo attheendofasentence. But there is a degree of the impoliteness yo shows. The degree depends on the person in the information. The second person used in the information, the degree is qulte high. The first person used, it gets lower. And the third person used, it becomes the lowest.