Tomorrow - Ending Explained

A central revelation of the series is the past life shared by Goo Ryeon and Park Joong-gil. They were a deeply in-love married couple hundreds of years ago. After Ryeon was abducted by barbarians and returned, she was unjustly ostracized by the village. The trauma and vicious rumors, coupled with the deaths her husband caused while seeking revenge, led her to take her own life with his dagger. In his grief, he also ended his own life. Because she committed suicide, their red thread of fate was severed. In the afterlife, Joong-gil's painful memories were sealed, causing him to subconsciously channel his grief into a cold, rigid hatred for those who commit suicide, explaining his intense antagonism toward Ryeon and her work.

The series finale resolves this tragic loop. Choi Joon-woong helps Joong-gil unlock his sealed memories. Realizing the truth, a guilt-ridden Joong-gil intervenes to save Ryeon from being dragged back to Hell for breaking afterlife rules, taking her punishment upon himself. This act provides them both with closure, though they do not reunite as a couple. Choi Joon-woong's contract ends, and he wakes up from his coma with no memory of his time in Jemadeung. However, the experience has fundamentally changed him; in his new life, he instinctively continues to help people on the verge of giving up, demonstrating the lasting, subconscious impact of his journey. The final scene shows the Risk Management team arriving at a case only to find Joon-woong has already saved the person, with the team smiling, knowing they will be reunited in several decades.

One area of interpretation revolves around the nature of the "severed" red thread of fate. The show establishes that suicide breaks this destined bond forever. However, both Goo Ryeon and Lim Ryung-gu encounter their key past-life connections (Park Joong-gil and his mother, respectively) in the afterlife. This has led to discussions about whether the rule is absolute. One interpretation is that the thread guarantees a happy romantic or familial union in reincarnation, and severing it only prevents that specific type of reunion, not any and all future encounters. Another perspective is that their unique circumstances as grim reapers, existing outside the cycle of reincarnation, place them in a loophole where they can meet but not truly rekindle their fated mortal relationship.