The “Treatise on the Observation of the Mind” handed down by either Bodhidharma or Yuquan Shenxiu is a foundational text that reveals the thought of the Northern Chan school. It has many variants, and if we can piece together how they intersect with and expand upon one another, we may gain precious insight into the history of the early Chan sects. Having said that, our understanding of the relationship between the variants of the text is muddied by several problems. For that reason, before writing this paper, I announced the publication of “Japan’s legacy: Fractured Debates on the Multiple Variants of the ‘Treatise on the Observation of the Mind’ as recorded in the New Edition of Kanazawa Bunko’s Extant and Partial Texts” at the East Asian Buddhist Studies Workshop this past May. In this thesis, I will clarify the relationship between variants of the “Treatise on the Observation of the Mind” produced in the three countries.