This thesis will consider ルand タ that were used in the scene of a perception change, speaking ago. As follows, I summarize the result that was divided into noun sentence, substantive verb sentence, テイルsentence. 1. I could figure out more clearly usage in the respect of ルandタ as analyzing according to a type of sentence 2. It is little different according to a type of sentence. But there is common in the case of using タ in the scene of a perception change, I can know the important factor that is the situation of speaking ago and the discovery scene 3. Even if the scene of a perception change, I clarify that ル is used to express the question about the scene under speaker’s very nose and the reason why ル was used in the state of repeat or progress. ル and タ in the scene that a change of perception accurred, from monitoring a state suddenly, will be considered in this thesis .