Previous research has highlighted the challenge of integrating renewable energies into electricity markets, particularly in maintaining market value amidst the increasing penetration. This paper builds on this foundation, exploring how renewable energies can be effectively promoted as a primary power source in Japan's electricity market post-grid parity. It delves into the trend of declining market value for renewables with increased market shares, influenced by their intermittency and non-dispatchability. With renewables reaching grid parity, the study, using the PyPSA-Japan-2050 Model, confirms the revenue cannibalization effect in Japan's solar, offshore, and onshore wind sectors, noting market value declines as penetration grows. We propose that enhanced carbon pricing policies could mitigate this decline, offering new strategies for sustainable energy development. We also consider the role of demand response mechanisms, such as electric vehicle batteries, in enhancing market value and stabilizing energy prices.