Maru's physical features always lean toward the “paler” side, always feel softer. Her charcoal-black hair, icy blue eyes, and slightly cool-toned skin stand out from the usual Hidaka family traits, making her look unique.
Scientifically, theres no true blue pigment in nature. Her low pigmentation makes her eyes highly reflective, so their color changes depending on the light around her. Sometimes they look sky blue, sometimes purple, and other times with a hint of pink or gold. It’s giving that her eyes hold the whole world inside them, or like a lil mirrors of it. Always reflecting its colors in different ways.
“The world reflected in her eyes is so colorful.”
“The eye is the window to the soul.”
as well as it's similar to Leo's birthday color. “Be yourself” and ”Be mine”
When working on album productions or other professional projects, Maru uses the pseudonym Kaito (かいと) or KaitoknP, written in hiragana to keep it gender-neutral despite its masculine tone. On the other hand, for her hobbies like drawing and writing, she goes by Mito (ミト), written in katakana to give it a less feminine feel. Both names are actually derived from her real name, Amaru (海十).
Because of this, no one realizes that Kaito and Mito are the same person—or that they are actually Leo's lover.
Leo made an offer to Maru to be his song cover designer, and she accepted it under the pseudonym "Kaito".
After NEWDI and Leo's official announcement of their romantic relationship, fans speculated that Kaito and Mito were the same person due to Kaito's designs having Mito's distinctive features. Maru also clarified under Mito's name that she was indeed working under the pseudonym Kaito, making fans even more shocked that Kaito and Mito were really the same person, and became Leo's lover.
Maru enjoys collecting CDs as it preserves memories for her. Whether it's CDs from her favorite idols, series, music, or movies, she finds satisfaction in building her collection. To her, CDs are like treasure chests of memories.
Sora describes Maru's color as "A sea with the glimmer of sunlight, without it being clear what the bottom looks like." The color changes when in the timeskip era, Sora describes it as "The sun surrounded by a bright blue sky, with rainbow clouds, iridescent colors adorning.”
Maru constantly forgets her stuff, mostly her phone to the point where the staff and other idols recognize hers.
Sometimes Maru refers to herself in the third person as she likes to talk to herself, either in a quiet place or with other people.
Maru has a habit of drooling when she falls asleep on her belly.
Her hearing is quite sensory so she is easily distracted by noises.
She has a sweet tooth but cannot eat much or she will get dizzy and nauseous.
Maru loves to use scents of lily, lemon, or white rose. She likes to wear unisex fragrances with flowery, powdery, and subtle scents. She is fine with some strong fragrances.
She is quite sensitive when tickled, specially on her waist, neck, and the area behind her ears.
People are often confused by the way she speaks so they think she's not talking about the actual topic.
Maru's hands are hotter than most people's. That's why her hands are often used as warmers, but her body gets cold easily.
Maru suffers from a nosebleed hereditary disease. This is quite bothersome, particularly during the summer. Her sense of smell is also quite sensitive.
Izumi was the first person from Yumenosaki she met. Maru fell in love at first sight with Izumi over his beauty on their first encounter, but it didn't last long.
When Maru was a young girl, she was often mistaken for a boy, as she was comfortable wearing boy's clothing.
Her surname used to be Ikeda (池田) from her father's side. However, due to family conflicts after her father's passing when she was 12 years old, she and her family chose to cut their relations off with Ikeda and replace them with Hidaka, her mother's surname. It was a burden for her to take on the famous Hidaka name, and that was one of the reasons she was bullied.
Maru is two years younger than most 3rd graders (!) but had the same grades as them before transferring to Yumenosaki due to the accelerated class program she took in elementary and middle school. Due to Yumenosaki's legal entry procedures and regulations, she had to 'drop a grade' and use the one-year probation period as an adaptation of the producer's special program. She became a second-year student and took the same classes as Anzu. Anzu took the producer program first and since Anzu was older than him, he would call Anzu with the suffix "Senpai" but was rejected. She then called her "Anzu-san".