Historically speaking, when Japan has connected with the world, Northeast Asian countries have served as geopolitical gateways. It would not be possible to think about Japan in relation to the wider world without taking into account the relationship with the Northeast Asian region. All the more because Japan has a long and close history with these neighboring countries, there are difficult diplomatic issues embedded in the relationship. On the other hand, such a long relationship entails many cultural similarities, which gives us hope that it will be possible to address issues that seem difficult to resolve.