The purpose of this study is to explore the ways in which successors obtain legitimacy and engage in proactive behavior in centuries-old Japanese family businesses that value tradition. Although business succession has typically been regarded as a critical issue in research on family businesses, the dynamic relationship between the innovative behaviors valued by next-generation leaders and the traditions valued by well-established companies has been largely overlooked. This case study demonstrates that successors experience the autonomy afforded by the marginal sector as well as the constraints of the central sector, and that practicable progress is made as a manager goes through the process of taking control from the previous generation of company leaders. Autonomy under guardianship (AUG) refers to the acquisition of legitimacy as a manager – that is, the accumulation of acumen and the expression of proactive behaviors as a manifestation of entrepreneurial activity. This study presents a conceptual model of autonomy under guardianship that describes the process of succession in Japanese family businesses that value tradition.