Kanae Otowa is a main character who serves as the landlady of the Otowakan, an old Western-style mansion she inherited from her grandmother. She is a first-year high school student and a member of her school's swimming club. Kanae was born to Kyougo and Himeka Otowa. Her father wasted the family fortune and eventually left, while her mother also departed, leaving Kanae to manage on her own for the most part. She was raised in the Otowakan by her grandmother, to whom she was very close; they once made a promise to hold another grand ball in the mansion, a promise that could not be kept after the house's mechanical organ stopped working. Following her grandmother's death, Kanae was left to take care of herself, a situation that changed only when the ClassicaLoids, created by her father, began arriving to live in the mansion.

Kanae has a diligent and notably stern personality, a direct result of her parents' long absence and the need to be strong for herself. This difficult upbringing has left her somewhat distrustful of the people around her. She is serious and strong-willed, possessing the resilience and tolerance required to accept the eccentric and freeloading ClassicaLoids into her home. Initially, she is annoyed by them, especially because they rarely pay their rent, and she often has to act as the only sane person reining in their chaotic behavior. However, through her daily interactions with them, she gradually begins to relax more and gain emotional strength. Despite her tough exterior, she has a hair-trigger temper and can become physically violent when frustrated, particularly with the resident Schubert and Mozart.

Her primary motivation stems from a deep, emotional connection to her family home, Otowakan. In the beginning, she intends to have the mansion demolished due to her father's debts and her own difficult memories. However, when a demolition team arrives, the broken mechanical organ begins to play, and Kanae breaks down in tears, pleading with the workers to stop, revealing that her desire to protect her grandmother's memories and the mansion itself is far stronger than she let on. Her role in the story is that of an anchor for the other characters; she is the landlady trying to manage the household, collect rent, and protect the mansion from both internal chaos and external threats. She is also very protective of Wagner, mistakenly believing him to be her long-lost younger brother.

Kanae develops key relationships with each of the residents. She maintains a general good relationship with Liszt, Tchaikovsky, Badarzewska, and Bach, whom she grows to trust. Her relationship with Beethoven (Beethes) and Mozart (Motes) is central, as they were the first to arrive and their actions directly impact her life. Sousuke Kagura, her friend, is a frequent visitor and another source of frustration, though he also offers support. Her relationship with Wagner is defined by her fierce, sisterly protection of him. Kanae experiences significant development throughout the series. She starts as an extremely strict and inflexible girl, afraid of what others might think of her for living with such odd characters. Over time, she loosens up, grows genuinely fond of the ClassicaLoids, and stops caring about the trouble they cause. She evolves from a lonely, distrustful teenager into a stronger, more relaxed individual who considers these bizarre beings her precious family.

Kanae does not possess Musik, the special power of the ClassicaLoids, as she is a normal human. However, she is able to be transformed by the Musik of others, such as when Schubert's power turns her into a fish. Her most notable ability is her unwavering determination and emotional resilience. She is a strong swimmer, a skill that is highlighted on several occasions.