Legal transplantation refers to the adoption, adaptation, or integration of legal norms, institutions, or systems from one jurisdiction into another. As a fundamental concept in comparative law, it plays a crucial role in shaping legal systems worldwide. In Japan, legal transplantation has been a defining feature of its legal history, characterized by successive waves of external influence and adaptation. This chapter examines the dynamics of legal transplantation, focusing on the challenges of integrating foreign legal frameworks within domestic cultural, political, and societal contexts. It explores how Japan has navigated these complexities by modifying transplanted legal concepts to align with indigenous traditions and values. Ultimately, Japan’s legal history demonstrates that the success of legal transplantation depends on the ability to contextualize and legitimize foreign legal structures within the recipient society, ensuring both functionality and acceptance.