We should be aware of the fact that numerous researches about Korean fact are not well reflected in grammar books and textbooks. This paper discusses the case of special postposition "eun/neun," which is particularly difficult to learn as an example. Existing grammar books and textbooks are reviewed, and the fact their contents are not through enough is pointed out. Among previous researches, ones that described the identity of "eun/neun," and its relevance to case marker in details are referenced, and in-depth research to re-organize these into grammar book is conducted. Based on this, an attempt to structure this Korean fact into more understandable contents is made. Basic characteristics are represented, and images to help understanding are attached. Then, characteristics of sentence meaning stemming out from these basic characteristics, and their connectivity to grammatical and pragmatical functions are shown. In addition, appropriate example sentences are presented to help understanding the case. The case’s basic contents are as follows: case marker is used when selecting one among several entities about one predicate. On the other hand, special proposition is used when selecting one from diverse predicates that has different values about selected subject. Due to this basic characteristic, case marker has a sentence meaning of point that designates a subject, and special proposition has a contrary undertone between a subject and a predicate. Furthermore, case marker is used grammatically as a subjective proposition, while special postposition is verbally used as a topic.