The abstractness of promissory note practice is a characteristic which explains that a promissory note can be accepted through various cause relations (or underlying transactions), but the right of it should be separated from the cause relations; thus, the cause relation and promissory note relation shall be strictly divided. The abstractness of promissory note practice is necessary to improve its transaction and to ensure its safe business. However, its abstractness should not be limited to the formal structure. Within the scope of the aims for its transaction improvement and guarantee of safe dealing, the cause relation can influence the promissory relation, considering the particular fairness between trading parties. In particular, currently, many argue that understanding the actual relation and promissory note relation differently can cause unfair or unreasonable outcomes. Thus, there are some circumstances of looking at the relation between those two. As a consequence, the strict interpretation of its abstractness can bring abuses or harmful effects on safe transactions. The Supreme Court used to generally presume that, where there is no explicit expression between the parties, the cause relation influences the promissory note relation as a conditional payment. Nevertheless,recently, the Court held that, when there is a specific circumstance, there should be a presumption in complete satisfaction. Therefore, the Court concluded that it should be decided based on what the specific circumstances which can overturn the presumption are, through clear and practical relations. This can be a method for solving the problem of unreasonableness from the strict interpretation of its abstractness in promissory note relations. In this perspective, it is noteworthy of considering the Court’s proper judgment on the interpretation based on “substitute for payment(in complete satisfaction)” for considering the specific circumstances, with related to the influence of promissory note relation on the cause relation.