Background: In anticipation of Japan's physician work style reforms scheduled for April 2024, which will restrict physicians' overtime duty hours to under 960 (Level A) or 1920 (Level C-1) hours per year, this study evaluates the potential impact on clinical resident physicians' training environments through the lens of residency program directors. Methods: A cross-sectional survey was administered to program directors from 701 facilities associated with the 2023 General Medicine-In Training Examination (GM-ITE), capturing responses regarding their planned level of overtime, perceptions of optimal working hours for training efficacy, and items considered as duty hours. Results: Out of the 701 facilities, 254 responded (36.2% response rate), with a predominant inclination towards adopting Level A (83.5%). A consensus emerged favoring 40 overtime duty hours per month as optimal, significantly lower than previous suggestions of 60-65 hours per week. The study also delineated the classification of activities as duty hours, with patient procedures and mandatory educational sessions identified as such, while self-improvement was largely not considered duty. Discussion: The findings indicate a substantial shift from previously recommended optimal duty hours towards a more conservative approach. This shift may reflect a proactive adaptation to upcoming regulatory changes and raises questions about the potential impact on the quality of clinical training. The distinction between educational activities and duty hours underscores the need for clarity within the impending work style reforms.