No Gain No Love - Ending Explained

The series finale reveals that Kim Ji-uk was actually the last foster child Hae-yeong’s mother took in before her dementia worsened. He stayed with her mother in secret to fulfill a promise, which is why he initially ghosted Hae-yeong after the wedding. Furthermore, the death of Hae-yeong's mother serves as the ultimate catalyst for Hae-yeong to stop 'calculating' her mother's love and realize that her mother's fostering was an act of extreme generosity that she now chooses to carry on. The 'breakup' in the final episode is a noble sacrifice by Hae-yeong to ensure Ji-uk isn't just staying with her out of a sense of duty or 'another promise,' allowing their eventual reunion to be a choice of pure desire.

Some critics have interpreted the ending not just as a romance, but as a parable of self-parenting. Hae-yeong's act of setting Ji-uk free is seen as her finally providing the 'selfless attention' to someone else that she felt she lacked from her mother, thereby healing her own inner child. Another reading suggests that the entire series is a satire of the institution of marriage, showing that a 'fake' marriage based on mutual respect and honesty is actually more successful than the 'real' marriages (like Hae-yeong's ex) which are built on infidelity and superficiality.