This paper demonstrates the relationship between the context in which yo is used and its prosodic features, specifically rising and falling pitches in the terminal intonation, and elucidates what underlies the choice of pitch types of yo in naturally occurring discourse context. In particular, I will argue that the function of yo, focusing on the information and/or expressing the speaker's insistive emphasis on what he or she is saying, varies depending on the choice of the pitch types in the context of discourse. I will also show that the speaker's insistive emphasis expressed by yo becomes significant specifically when the speaker's bias toward the mutual understanding with the addressee is involved.