Digital Therapeutics (DTx) is emerging as an innovative therapeutic approach in healthcare systems. This advancement is particularly significant in Japan, which faces critical healthcare challenges including a rapidly aging population, rising medical costs, and a shortage of healthcare professionals. While studies have indicated that user acceptance is a crucial factor in the successful adoption of such novel technologies, empirical research on DTx acceptance, particularly in the Japanese context, remains limited. This study aims to identify the factors influencing DTx acceptance in Japan by utilizing the UTAUT model, which has been widely validated in technology acceptance research. We conducted a survey of 1,023 users who had experience with approved DTx applications in Japan. Results from covariance structure analysis revealed that Performance Expectancy and Social Influence significantly affected DTx acceptance. Additionally, qualitative analysis of free-text responses confirmed that recommendations from healthcare professionals and acquaintances and expectations of therapeutic effectiveness were primary factors influencing acceptance. These findings provide practical implications for developing effective strategies to promote DTx implementation in healthcare systems.