The purpose of this study is to investigate discourse characteristics of the Japanese produced by superior-level non-native speakers. We first considered the ACTFL-OPI and CEFR rating scales and reviewed previous research. We then extracted the factors that characterize superior-level speakers and divided them into two categories: those related to discourse quality and those related to consideration for listeners. On the basis of OPI interview data, we compared these factors in the speech of superior-level speakers and that of advanced-level speakers by applying a text mining technique. The results revealed the following characteristics of superior-level speakers: (1) they use more ko- type anaphoric demonstratives than advanced-level speakers, (2) they use more sentence-final particles that function as utterance mitigation, (3) they utilize varied fillers, (4) they use attempt expressions to demonstrate that they are seeking appropriate words.