The story of "Mercy for None" begins with Nam Gi-jun, a former enforcer for a criminal gang, who has left his past behind after an incident eleven years prior. He has been living a relatively normal life, away from the world of crime. However, his younger brother, Nam Gi-seok, a top official in the Juwoon Group, is brutally murdered. This event forces Gi-jun back into the world of crime to uncover the truth and seek revenge on those responsible.

Gi-seok's death sparks outrage among those who cared for him, but the chairman of Juwoon is reluctant to seek revenge for his right-hand man. Gi-jun, however, has no such reservations and begins investigating his brother's murder. He is thrust into a world of violence and betrayal, which leads him to Jun-mo, the son of Chairman Gu of the Bongsan Group. Jun-mo is known for causing chaos within his father's organization and rarely faces accountability for his actions.

As Gi-jun delves deeper into the mystery, he discovers that Jun-mo had hired foreign thugs to kill a fellow Bongsan manager who was encroaching on his share of the business. Chairman Gu, wanting to discipline his son without appearing to do so, asks Chairman Lee for help. Lee agrees to intervene in exchange for Gu's assistance with some land acquisition troubles. Lee sends Gi-seok to rough up Jun-mo, but Jun-mo retaliates by ordering a hit on Gi-seok.

When the truth about Jun-mo's involvement in Gi-seok's murder surfaces, it threatens the peace between the Bongsan Group and the Juwoon Group. The two groups turn against each other, with Juwoon emerging victorious, thanks in part to the help of Juwoon's prosecutor son, Lee Geum-son, who greenlights a raid on the Bongsan Group.

Gi-jun's mission to find justice for his brother leads him to confront Jun-mo. Despite realizing that Jun-mo's hired thugs did not directly kill his brother, Gi-jun decides to kill Jun-mo because he had ordered the hit. Gi-jun fights through dozens of men to reach Jun-mo and ultimately kills him.

After Jun-mo's death, Bong-san, who had been investigating the conspiracy behind Gi-seok's murder, discovers that the order to kill Gi-seok came from within Juwoon's own ranks. Bong-san suspects Yeong-Do but is told to suspect Juwoon's own son instead. Meanwhile, the prosecution raids Bongsan's base, creating chaos.

In the final stages of the series, Juwoon kills his old friend Bongsan to protect his son. Gi-jun, having discovered the truth behind his brother's death, continues his quest for revenge. However, Gi-jun ultimately dies in the final episode of the series.

Throughout the series, Gi-jun's actions are driven by his desire for vengeance and his need to uncover the truth about his brother's murder. His journey is marked by violence, betrayal, and a complex web of alliances and rivalries within the criminal underworld.

The ending of Mercy for None (2025) concludes with Nam Gi-jun avenging his brother Nam Gi-seok's murder by killing Gu Jun-mo, the chairman's son, after uncovering a deep conspiracy behind the killing. However, Gi-jun dies in the final episode, closing his violent quest for justice with his own death.

In the final sequence of Mercy for None, the story unfolds as follows:

Gi-jun, having returned from exile due to his brother Gi-seok's brutal murder, relentlessly pursues the truth behind the killing. Early on, it is revealed that Gu Jun-mo, the reckless son of the Bongsan Group chairman, ordered a hit on Gi-seok through an underground organization run by Seong-Won. This was part of a chaotic power struggle within the criminal underworld.

As Gi-jun digs deeper, he confronts Jun-mo directly. Despite learning that Jun-mo's hired thugs were not the actual killers of Gi-seok, Gi-jun kills Jun-mo in a violent confrontation after fighting through numerous men. This act is Gi-jun's personal retribution, symbolizing his refusal to let the conspiracy go unpunished.

Meanwhile, Bong-san, a former colleague and friend of Ju-woon (Gi-jun's brother's boss), investigates the murder independently. He discovers that the order to kill Gi-seok came from within Ju-woon's own gang, implicating internal betrayal. This revelation escalates tensions between the Juwoon and Bongsan groups, leading to a breakdown of their fragile peace.

In a climactic moment, Ju-woon kills Bong-san to protect his son Jun-mo, showing the ruthless lengths the crime lords will go to preserve their power. However, Ju-woon's victory is short-lived as the conflict spirals out of control.

The final scenes focus on Gi-jun's fate. After exacting his revenge by killing Jun-mo, Gi-jun succumbs to his injuries or the consequences of his violent path and dies. His death marks the tragic end of his quest for justice and revenge, closing the narrative on a somber note.

Fates of main characters at the end:

• Nam Gi-jun: Dies after killing Jun-mo, ending his violent mission for vengeance.
• Gu Jun-mo: Killed by Gi-jun in retaliation for his role in Gi-seok's murder.
• Nam Gi-seok: Murdered early in the series, his death triggers the entire revenge plot.
• Bong-san: Killed by Ju-woon while investigating the conspiracy.
• Ju-woon: Survives but loses his friend Bong-san and faces the collapse of his criminal alliances.

This ending scene-by-scene narrative highlights the brutal cycle of violence and betrayal within the criminal underworld, showing how Gi-jun's pursuit of justice ultimately consumes him, and how power struggles destroy longstanding relationships.

The TV show Mercy for None (2025) does not have a traditional post-credit scene. Instead, the series ends with a poignant final moment where the protagonist Gi-jun, severely wounded after his final confrontation, sits alone by a fire and imagines his deceased brother Gi-seok sitting beside him. They share a quiet, dreamlike conversation about quitting their violent lives and starting fresh, a life Gi-jun always longed for but never had. This scene symbolizes Gi-jun finding peace in death, finally reunited with his brother in his mind before he dies. The show closes on this somber, reflective note without additional scenes after the credits.

This final moment serves as a metaphorical closure rather than a separate post-credit teaser, emphasizing the emotional cost of revenge and the tragic resolution of Gi-jun's quest for justice.

Nam Gi-seok's murder was orchestrated as part of a complex conspiracy involving the Bongsan Group and the Juwoon Group. Specifically, Gu Jun-mo, the chairman's son of the Bongsan Group, hired foreign thugs to kill a Bongsan manager, which led to retaliation involving Gi-seok. Jun-mo took out a hit on Gi-seok in retribution, but the deeper conspiracy was uncovered by Bong-san and Gi-jun, revealing who ordered the murder and why by the series end.

Gi-jun, the protagonist, is the brother of the murdered Nam Gi-seok, while Jun-mo is the son of the Bongsan Group chairman and a disruptive figure within his family business. Their relationship is antagonistic; Jun-mo's actions indirectly lead to Gi-seok's death. Gi-jun ultimately kills Jun-mo after a violent confrontation, even though he realizes Jun-mo's hired thugs were not the ones who directly killed his brother. This conflict escalates the tension between the two crime groups.

Bong-san is a character who suspects there is more to Gi-seok's death than initially apparent. He conducts his own investigation into the murder, uncovering a shocking conspiracy that ties into the larger conflict between the Juwoon and Bongsan groups. His findings contribute to revealing the truth behind the murder and the power struggles involved.

Gi-jun had severed ties with his gang eleven years before the events of the series, seeking a more normal life. However, his brother's murder drags him back into the violent world he left behind. His former skills and reputation as a highly respected gang member enable him to navigate the dangerous underworld, fight numerous adversaries, and pursue a relentless path of revenge and justice for his brother.

At the end of Mercy for None, Gi-jun dies. After uncovering the conspiracy behind his brother's death and killing Jun-mo, Gi-jun's rogue mission concludes with his own death in the final episode, marking a tragic end to his quest for vengeance.

The TV show Mercy for None (2025) is not family friendly; it is rated TV-MA, indicating it is intended for mature audiences aged 17 and older.

Potentially objectionable or upsetting content for children or sensitive viewers includes:

• Violence and crime-related themes, as the story revolves around a former gangster seeking revenge, which likely involves intense action and violent scenes.
• Mature and dark themes such as gang conflicts, death, and possibly graphic or disturbing moments related to crime and revenge.
• The TV-MA rating suggests the presence of strong language, violence, and possibly other adult content that is unsuitable for younger viewers.

No specific spoilers are revealed here, but viewers should expect mature content that may be distressing for children or sensitive individuals.