Nanase Yamamura, also known as Nanase Fujikura in the original manga and Nanase Kishibe by birth, is a central figure in the story of Rohan at the Louvre. She is a young Japanese woman of striking appearance, with a slender build and long, dark, flowing hair that she sometimes ties into a ponytail. In the live-action adaptation, she is referred to as Nanase Yamamura after her marriage to the painter Nizaemon Yamamura.

Her background is intertwined with a centuries-old tragedy. Born as Nanase Kishibe, she was the wife of Nizaemon Yamamura, an artist who became obsessed with creating the perfect black pigment. When Nanase discovered a black sap from a sacred ancient tree, she brought it to her husband, believing it would fulfill his artistic vision. This act inadvertently set off a chain of events leading to Nizaemon cutting down the tree, an offense punishable by death. When officials came to arrest him, Nanase tried to protect her husband and was struck down, dying from the violence. Consumed by grief and rage, Nizaemon killed the officials and, using the cursed pigment, painted a portrait of his wife that became imbued with his hatred and despair.

In terms of personality, Nanase carries a deep sense of sorrow and guilt. She is gentle and melancholic, burdened by the tragic outcome of her actions and the curse that has trapped her spirit for centuries. Despite her ethereal and mysterious demeanor, she is driven by a protective instinct, especially toward her descendant, Rohan Kishibe. Her primary motivation is to atone for the past and to prevent anyone else, particularly Rohan, from being destroyed by the cursed painting she helped bring into existence.

Within the story, Nanase serves as both the catalyst for the plot and a key figure in its resolution. She first appears as a young woman renting a room at the inn owned by Rohan's grandmother when Rohan is a teenager. During this time, she tells him about the existence of the world's blackest and most evil painting, which she claims is held at the Louvre. This encounter leaves a lasting impression on Rohan. Later, after disappearing from his life, she reappears as a spirit bound to the painting. At the climax, when Rohan is under attack by the supernatural forces of the cursed artwork, Nanase intervenes, physically restraining the vengeful spirit of Nizaemon and urging Rohan to forget everything to save himself. This act of sacrifice allows Rohan to escape and ultimately break the curse that had held her spirit captive.

Her key relationships are centered on two men. With her husband, Nizaemon Yamamura, her bond is one of tragic love and shared ruin; her desire to help him led to both their deaths and the creation of the cursed painting. With Rohan Kishibe, she shares a familial bond as his ancestor, and she develops a protective, maternal concern for him. When Rohan, as a young man, begins to draw her, she fears he is repeating Nizaemon's fatal obsession and destroys his artwork in a desperate attempt to sever that connection and shield him from the same fate.

In terms of development, Nanase begins as a ghostly figure haunted by her past, unable to move on. Through her interactions with Rohan and the eventual destruction of the cursed painting, she finds a measure of redemption and release. At the story's end, after Rohan reads her memories using his power, he reassures her that her presence in his life was meaningful, allowing her to finally find peace and disappear with a smile.

Nanase possesses no supernatural abilities of her own. Her notable attributes are tied to her existence as a spirit, allowing her to appear and interact with the living world, particularly in locations connected to her past or to the cursed painting. The painting itself, which she inspired, contains a powerful curse capable of manifesting the deepest regrets and sins of those who look upon it, leading to their demise. Nanase's enduring will and love, however, give her the strength to defy that curse in her final act to protect Rohan.