This paper focused on the poor life and identity of Korean residents in Japan appearing in Son Chang-seop’s Yummeng. The difference between this discussion and the existing discussion is that it referred to Berry’s cultural transformation model, viewed Koreans in Japan as subjects of speech, not as objects of reproduction, and finally looked at Son Chang-seop’s inner landscape through the focus speaker “I.” Japan, which was an unequal multi-ethnic country, excluded other peoples who were the same people in the past based on its new identity as a single nation state when it created a new country after the defeat. As a result, Koreans in Japan were forced to exist as invisible minorities for a long time in Japanese society. Senior citizens Choi Won-bok and Koichi Takamura (Ko Kwang-il), who are the first generation of Koreans in Japan, show separation and assimilation in the cultural transformation model. The contrast between Choi Won-bok and Koichi Takamura (Ko Kwang-il) is realistically revealed through food. In light of the fact that the original taste for food not only reflects identity but also constitutes cultural identity, the difference between Choi Won-bok and Koichi Takamura (Ko Kwang-il) in food directly shows the difference of the cultural transformation model they experience in Japan. Unlike the first generation of Korean residents in Japan, the second generation of Korean residents in Japan shows the appearance of marginalization. The second generation of Koreans living in Japan can be said to be a generation separated from their native culture. Originally, young immigrants have a weaker cultural identity of their country of origin than older immigrants, and Koreans in Japan are more likely to be far from their native culture due to the fact that their settlement is a colonial host country and their home country is divided into the north and south. In addition, they were forced to be further alienated from their native culture due to the Korean government’s policy of considering Koreans living in Japan only as a subject of alertness and surveillance from the time of liberation to the 1980s. Next, as a result of Japanese society excluding Koreans living in Japan based on their racial superiority, Korean Residents in Japan fail to establish a normal relationship with Japanese culture. As such, the second generation of Korean residents in Japan, who are alienated from both their native and mainstream cultures, shows extreme marginalization. “I,” the focalizer of Yummeng, is also a marginalized existence, but it is distinguished from other Korean residents in Japan in that the marginalization at this time appears from the inside rather than the background of a specific scene of life. “I” can be said to be a divided existence of consciousness and unconsciousness, conditional and unconditional. In terms of impulse and instinct, they reject ‘Japanese things’ and aim for ‘Korean things’. However, in terms of consciousness, they think critically of South Korea even while comparing it with Japan. Due to this division, the path given to ‘I’ is not to become a Korean or a Japanese, but to not become a Korean or a Japanese. Such circumstances are compressed by the appearance of “I,” who wanders around downtown Tokyo alone with mixed feelings after returning Choi Won-bok, who returns home from Tokyo Station in the last scene of the work. Until now, the relationship between Korean society and Koreans living in Japan has been a one-sided relationship between subject and object. However, it can be seen that the reproduction of Koreans in Japan through the focus speaker “I,” which is a divided Korean resident in Japan, has a different context from the general reproduction so far.