Realistic mathematics education (RME) has proven to be an effective model for mathematics elsewhere. However, students and teachers still grapple to confront the circle equation to learn and teachers to teach. This study explored students' didactical phenomenological discourses in the circle equation as an alternative. The mixed methods research design was used to collect both quantitative and qualitative data from 50 senior high school students purposely selected from one senior high school. The instruments of data collection were the questionnaire and interview guide. The purpose of the questionnaire and interview guide was to validate and corroborate. The quantitative analyses contain categorical independent and continuous dependent variables and were explored by reliability statistics, simple and multiple analysis of variance tests of independence. On the other hand, the qualitative transcriptions of students' own perceptions. The results on the types of equations showed low didactical phenomenology as many variables fell below the .20 minimum internal consistency's criteria. However, the results of the tasks showed high acceptable didactical phenomenology. We therefore concluded that RME could be extended to other domains of mathematics. Thereafter, comprehensive recommendations were advanced for theory, method, research, practice, policy, and context.