"Kingdom Hearts: 358/2 Days" is a manga adaptation of the Nintendo DS game of the same name, expanding on the events of the "Kingdom Hearts" series. The story centers on Roxas, a boy who becomes a member of Organization XIII, a group of Nobodies seeking to reclaim their lost hearts. Roxas, who wields the Keyblade, is unique among the members as he is the Nobody of Sora, the series' protagonist. The narrative explores Roxas's journey as he grapples with his identity, purpose, and the nature of his existence.

The plot unfolds through Roxas's daily missions alongside Axel, his close friend and fellow Organization member, and Xion, a mysterious girl who also wields the Keyblade. The trio forms a strong bond, sharing moments of camaraderie and joy despite the Organization's cold and calculating environment. However, tensions rise as Xion begins to experience memory lapses and physical deterioration, revealing her true nature as a replica created to absorb Roxas's powers. This revelation strains their relationships and sets the stage for a tragic confrontation.

As the story progresses, Roxas learns more about his connection to Sora and the Organization's true motives. The Organization manipulates Roxas and Xion, using them as tools to further their goal of completing Kingdom Hearts, a source of immense power. Roxas's growing awareness of his role as a pawn leads to internal conflict and a desire to break free from the Organization's control. The climax sees Roxas and Xion forced into a battle, with Xion sacrificing herself to ensure Roxas's survival and the eventual restoration of Sora's memories.

The manga delves into themes of identity, friendship, and the consequences of manipulation, offering a deeper exploration of Roxas's character and his relationships with Axel and Xion. The narrative bridges the gap between "Kingdom Hearts: Chain of Memories" and "Kingdom Hearts II," providing context for Roxas's role in the broader series. The story concludes with Roxas leaving the Organization, setting the stage for his eventual confrontation with Sora in "Kingdom Hearts II." The manga adaptation retains the emotional depth and complexity of the original game while presenting the story in a visually engaging format.