This study analyzed the inserted notes that appeare in Seokbosangjeol and Wolinseokbo. And based on the analysis, the reason that NP imbedding prefinalending ``-O-`` does not appear in the place where its hould appear was examined in consideration of then atureand character isticsof the inserted notes. As the characteristics of the Korean language in the Middle Ages, there are many cases in which the sentence structure where a noun before a predicate has a determiner ending with the postposition being omitted appears. In these cases, the pre-connection of the prefinal ending ``-O-`` is not made. It seems that this is used in the form of being recognized as the same as the predicates that follow. In other words, it can be interpreted that the prefinal ending ``-O-`` does not appear because the condition in which the prefinal ending ``-O-`` is used should be a clause, but it is recognized as a phrase. Although it cannot be said definitely since all the literatures in the 15th century were dealt with, the clue to the reason that the prefinal ending ``-O-`` does not appear when it should appear can be found in the analysis on the inserted notes.