Menō Matsuyama is a character introduced in the second half of the White Album anime adaptation, serving as a pivotal figure whose past actions are revealed to have significantly influenced the present story. She is an original character created for the television series and does not appear in the original visual novel. As a musician, Menō is affiliated with the talent agency M&M Music.

In terms of background, Menō is the eldest daughter of Itsuki Kanzaki, the president of M&M Music, and the older sister of Mana Mizuki. She is also a distant relative of the main heroine, Yuki Morikawa. Her connection to the protagonist, Tōya Fujii, stems from an encounter ten years before the main story. During that childhood meeting, Menō cast a hypnotic suggestion on the young Tōya, implanting in his mind the idea of perceiving women as goddesses while also sealing his early memories. This act, born from her jealousy towards Yuki, whom her sister Mana deeply admired, inadvertently became the catalyst for many of the complicated relationships and emotional struggles that Tōya experiences throughout the series.

Personality-wise, Menō often adopts an older-sister demeanor towards Tōya after their reunion, frequently visiting his apartment and inserting herself into his daily life. Her motivations are complex and not rooted in romantic interest. Rather than seeking a romantic partner, her primary desire appears to be a longing for genuine family affection. Observing that Tōya has become entangled with her mother (as a client), her sister Mana (as a tutor), and her professional rival Rina Ogata, Menō finds him to be an endlessly fascinating subject and a living consequence of her past mistake. Her actions are largely driven by a sense of responsibility and a desire for atonement; she aims to undo the curse she placed on him a decade ago, hoping to mend the fractures she caused in his relationship with Yuki and, in doing so, find a path to reunite her own estranged family.

As an artist, Menō is a performer signed to her mother's agency, distinguishing herself as one of the emerging idols in the competitive music industry. She plays a crucial role as a key person in the overarching narrative, directly linking the past to the present. Her presence often carries an air of mystery, and she has the ability to influence events by holding the key to Tōya's lost memories. A notable aspect of her history is that she previously had a relationship with Tamaru, a senior student at Tōya's university, adding another layer to her connections within the story. Throughout the second season, Menō develops from a seemingly enigmatic figure into a character who actively works to resolve the discord she originally created, providing a pathway for the central characters to find closure.