Ren Amamiya, in "Proof of Justice," grapples with the aftermath of Goro Akechi's death. Discovering a crossword puzzle magazine at Café Leblanc containing Akechi's handwritten solution for "Seigi no Akashi" (Proof of Justice), he embarks on an investigation through Tokyo's snowy streets to decipher its meaning. This quest triggers reflections on their past encounters and unresolved conflicts.

Demonstrating persistence and contemplation, Ren retraces locations significant to their rivalry despite the harsh cold. Flashbacks reveal his complex view of Akechi, acknowledging their adversarial history while privately wrestling with grief and unanswered questions about justice and redemption. His solitary journey underscores self-reliance and the emotional weight of Akechi's absence.

The narrative focuses on Ren's internal conflict, conveyed through his silent determination to understand Akechi's final message, emphasizing the connection that existed beyond overt hostility. No other allies or Phantom Thieves activities appear, isolating Ren's personal processing of loss and the symbolic legacy of their confrontation.