Understanding how young people envision happiness and ideal cities is essential for designing human-centered smart urban futures. This study explores the well-being perceptions of Japanese youth aged 16–24 (N = 2,437), using an online survey that included both closed and open-ended questions.

Topic modeling and cluster analysis revealed three dominant value orientations: Connection and Belonging, Freedom and Autonomy, and Stability and Security. These themes reflect diverse urban preferences grounded in emotional, social, and existential needs. While no urban feature showed strong statistical significance in predicting well-being, nature, safety, and cultural elements appeared consistently relevant.

Narrative responses highlighted symbolic openness and emotional nuance, suggesting the importance of environments that foster flexibility and non-prescriptive engagement—what we refer to as “slack fields.” Though not directly measured, such affective dimensions may complement spatial metrics in digital twin and urban analytics systems.

This study contributes to value-based urban design by integrating youth perspectives and affective indicators into the smart city discourse. Its findings support more inclusive, emotionally resonant planning frameworks that go beyond technical efficiency.