Achieving carbon neutrality by 2050 presents both a technological and socio-economic challenge for Japan, a nation characterized by high energy import dependency, a declining and aging population, and regional disparities in renewable energy resources. This chapter presents an in-depth scenario analysis using an improved Glocal Century Energy Environment Planning (G-CEEP) model, which incorporates socioeconomic projections, energy technology modules, and regional renewable potential assessments. The model enables dynamic simulation of demand-supply evolution under varying assumptions, highlighting key temporal phases and spatial patterns of decarbonization. Results suggest that while the 2050 net-zero target is technically feasible, it will require differentiated strategies: early deployment of building efficiency and on-site renewables, mid-term expansion of imported clean energy, and late-stage reliance on flexible technologies such as hydrogen, biomass, and long-duration storage. The chapter also emphasizes the importance of addressing energy mismatches and regional equity in transition planning. These insights provide critical guidance for policymakers aiming to design adaptive and locally optimized decarbonization pathways in Japan.