Japan stands as a rare country in which ESD has been incorporated as mainstream policy. However, looking back on the United Nations Decade of Education for Sustainable Development (UNDESD), ESD has not brought about the transformation in Japan that one expects ESD to aim for, despite this support at the policy level. The cause may be that pouring the "new wine" of ESD into the "old bottle" of the traditional educational system has diluted the dynamism contained in ESD. Both "shallow ESD" and "deep ESD" exist. The former stems mainly from widely shared interpretations of ESD that emphasize the overlap and connections with existing school subjects and types of education. The latter is needed to avoid this loss of dynamism and to gain access to the full potential of ESD. Holistic educational approaches that replace conventional ones, as well as system-level transformation, are indispensable to realize this "deep ESD."