Hae-jo is the central character in "Mr. Plankton." He was born as a result of an incorrect artificial insemination, which led to him living a life without a true family. Upon discovering that he is terminally ill, Hae-jo takes Jae-mi, a woman known for her incredible bad luck, on a final journey with him. His ultimate goal is to locate his biological father before his time runs out. Hae-jo is characterized by his resilience, resourcefulness, and a strong sense of justice. He often stands up for those who are wronged and remains hopeful despite his difficult past. As he faces the end of his life, Hae-jo seeks to create meaningful connections and find a sense of closure.