Article 242 of the Civil Code in Japan states that “the owner of real estate shall acquire ownership in a Thing that has been attached thereto as its accessory.” However, it is not necessarily clear in what sort of situations certain objects are determined to be attached to real estate as an accessory. Thus, various interpretations regarding the circumstances in which something and another thing are recognized as “being attached” have been asserted. Nevertheless, none of these interpretations provide any uniform understanding of court cases from the Supreme Court. While there are various cases discussing whether the rule of attachment to real estate is applicable or not, it has been pointed out that measuring whether something is attached or not with a single scale is indeed problematic. However, reflecting on the fundamental principles of interpretation and examining the requirements given in Article 242 of the Civil Code and then adding the distribution of the burden of proof, it is perhaps possible to understand the determination of the Supreme Court in a uniform fashion. From this perspective, this study explores the possibility of an interpretation that allows for a uniform understanding of Supreme Court rulings.