Abstract: Japan's prohibitive regulatory system for insurance sales behavior concurrently governs the conduct of both insurance companies and sales agents during information provision and throughout the sales process. For insurance companies, the regulations prohibit practices such as the false disclosure of material facts, misleading product comparisons, and the conclusive judgment on uncertain matters. For sales agents, the prohibitions address issues such as impeding policyholders' disclosure obligations, engaging in improper cross-selling, and offering undue special benefits. The evolution of this regulatory framework is evidenced by the integration of the Insurance Business Act with related normative documents and legal provisions, facilitating a shift from a penalty-oriented model to a multi-layered "elements–effect" procedural regulatory paradigm. This system exhibits self-referential characteristics and, when combined with proactive regulatory measures, shapes the normative conduct of insurance sales: the "legal" code is structured through obligations of intent determination and disclosure, while the "illegal" code emphasizes the exclusion of undesirable behaviors. The Japanese model suggests that domestic legislation should move beyond its current abstract framework by refining the typified standards of prohibitive clauses and establishing a dynamic linkage between legal norms and industry guidelines. Through such functionally differentiated institutional design, a dynamic balance between regulatory compliance and market vitality in insurance sales can be achieved.