Kanaru Morimoto is a student at Naginomori Gakuen high school in Ayanagi City and a classmate of Shin Kanzato. She has a reserved and quiet demeanor, often coming across as somewhat timid. Her appearance and manner are noted to have the purity of a young princess, though she can also be a little spontaneous. Academically, she achieves high marks, particularly excelling in language and speed reading over scientific subjects.

In her daily life, Kanaru is a close friend to Shin, Megumi Kayano, and Takuro Sakakiba. While she struggles to voice her feelings openly, she steadily develops romantic feelings for Shin as the story progresses. However, Kanaru is a deeply troubled individual. She suffers from occasional memory lapses, finding herself in unfamiliar places with no recollection of how she arrived there. This is linked to her involvement with a dangerous practice known as kagenuki, or shadow extraction. The process, which forcibly invokes a Persona, produces a euphoric sensation similar to taking a drug, and Kanaru becomes addicted to this feeling. Among those who abuse kagenuki, she becomes known by the name Mori. Her addiction reaches a critical point where she experiences severe withdrawal symptoms, endangering her friendships and prompting an intervention from Shin and the others. Shin eventually slaps her in an attempt to make her confront the severity of her condition, which becomes a turning point for her.

Kanaru's personal history is marked by growing up in a nursing facility or orphanage with a friend named Mayuri Yamazaki. This past is intertwined with a much larger and more tragic revelation: Kanaru is not a normal human. She is an android, a creation of Keisuke Komatsubara, designed for the purpose of spreading the kagenuki trend and gathering information on Persona users for the organization known as Marebito. Commanded by specific keywords, she can switch personalities, shifting from her gentle self to an emotionless, robotic state loyal to her creators. Members of Marebito refer to her as a "doll," believing she has no true will of her own.

Despite her artificial nature, Kanaru demonstrates a unique and powerful ability: she can invoke two different Personas. Her controlled personality, loyal to Marebito, summons a Persona named Ashtoreth, which is similar in form to those used by the organization. However, after making the heartfelt decision to overcome her addiction and reject a proposition for kagenuki from her old friend Mayuri, she breaks down in a park. There, Shin finds her, and his comfort triggers the awakening of her own true Persona, Astarte. Unlike most humanoid Personas in the series, Astarte has a much simpler appearance, resembling a jellyfish. Megumi Kayano comments that this is because it is a "baby Persona," reflecting Kanaru's own nascent and genuine strength. Later, Shin uses Abel's ability to separate the false Persona, Ashtoreth, from her.

Her journey is one of seeking agency and identity against a predetermined fate. Even as she forms genuine friendships and falls in love, she learns that her memories, relationships, and much of her life are built on illusions created by Komatsubara. Ultimately, she is set to automatically deactivate, her artificially constructed lifespan far shorter than a human's. Kanaru spends her final moments peacefully in the company of Shin, having severed her ties to Marebito and asserted her own will. After her death, her friends, Megumi and Takuro, are able to summon her Persona, Astarte, one last time during the final battle, a testament to the lasting impact she had on them.