This study assesses Japan's emission pathways aimed at net-zero emissions by 2050, as implied by the Paris Agreement's global climate goal of pursuing efforts to limit the temperature rise to 1.5 °C. Based on a scenario analysis performed using AIM/Enduse [Japan], Japan's energy supply sector requires a radical transformation, including reliance on carbon dioxide removal options such as bioenergy with carbon capture and storage (BECCS) to attain net-zero emissions by 2050 without substantial social changes. By contrast, the gap between the 1.5 and 2 °C scenarios is relatively moderate in demand sectors. The building sector may need to be decarbonized even in the 2 °C case, whereas the transportation sector will face additional challenges, such as electrification and penetration of biofuel, in the 1.5 °C case. Reaching net-zero emissions by 2050 is a huge challenge, since the price of carbon in the net-zero emissions case increases by a factor of four or five over that in the 2 °C case. Moreover, the absence of early action as well as limited use of low-carbon energies would considerably add to the burden. Given these challenges and uncertainties, the potential of other mitigation options, such as drastic social change, large-scale afforestation and international emissions trading, merits consideration.