This article aims to study how cognitive factors, such as emotions, get involved in the extension and variation of folk tales, with special focus on the “ONUI-HIMNAEGI” (the trial of strength between brother and sister) tale. This tale produces a controversial discourse, as narrators’ attitudes toward the main characters — the defeated sister and the winning brother — vary in different versions. I focused on emotions and experiences according to cognitive narrative studies and reviewed several versions. Versions that can be regarded as ‘mistakes’ of narrators’ oblivion or confusion can turn into examples for explaining narrativity of emotions. The grudge of a victimized sister becomes the “cause” for other events or increases influence of certain evidence of legends, which leads to extending transmission of tales. On the other hand, when it comes to certain type of versions in which the sister gives up on her own for the sake of the brother, her emotions are relatively hidden. Instead, we can find condolences as the collective emotion in the male character. Furthermore, variations on transmission also occur when narrators’ experience of related sites comes into the narrative. Through these suggestions, some versions show examples deviating from the existing plots. However, some versions are chosen to be ‘narrated’ because they are ‘tellable’ to certain narrators. Therefore, I suggest that what is ‘tellable’ from the narrators’ point of view be continually discussed according to existing versions of the tales.