Hikari has black hair with a blue tint and blue eyes, and strongly resembles her brother, Tsubasa. She is tall for her age and overpowers Ema and most of her classmates. She wears the standard Alice Academy Troupe uniform.
Hikari is stubborn, short-tempered, and tomboyish. She tolerates bullying from other students whom she perceives as spoiled and unimportant. Although she is curious of the depth of an Alice and the difference between Alice users and non users, she strives to unite the two by joining together with Ema and creating a miracle that the two can be compatible. Hikari is immediately drawn to Ema's beauty and strong voice, and despite the initial shock of finding out Ema is really a man, she continues to admire him and seems to be developing feelings for him.
When Hikari was a little girl, Tsubasa was taken away from their parents by the Academy when his Shadow Alice was discovered. Hikari was then sheltered by her parents, even when it was obvious she didn't possess an Alice. While she was at a dojo session, her parents died in a car accident, and Hikari was left an orphan and cared for by her cousin's family.
Twelve years after Tsubasa left for the Academy, Hikari is walking through the city when she hears about the Alice Academy Opera Troupe. Thinking that joining will get Tsubasa to notice her and reunite with her, Hikari takes the application exam and passes, which amazes her due to her terrible skills in singing and dancing. With her cousin, Hikari arrives at the music school and sees the top student, Ema Shinomiya, give the opening speech, and she becomes enchanted by Ema's voice. Hikari learns more about the music school's history and a Sisters Bond, in which an Older Sister picks and forges a partnership with a Little Sister, from the principal, Narumi. Hikari is immediately bullied by the other students for her poor acting skills but she ignores them. After class, she runs into Ema, who is fleeing from a group of boys but Hikari easily beats them. However, Ema's shirt if pulled apart and revealing Ema is really a boy, and Hikari is shocked to learn from Narumi that Ema disguises himself as a girl to protect himself because his Alice is targeted and thus puts his life at risk. Threatened with being expelled if she reveals this secret, Hikari agrees to keep quiet and not cause trouble. Hikari asks Ema why he always dresses as a girl and he explains he can't leave the school as long as he is in danger but has chosen to live a woman's life to make a better oath for himself. The next day, Hikari learns from Aoi Hyuga about the Sisters Bond and is surprised when Ema wants her to become his "little sister", which puts her at risk of Ema's admirers. Hikari arrives late for class and is stuck with the cleaning as punishment, which the other students hope will make her quit the school. Hikari does try to escape but to find Tsubasa herself. She tries to climb the high wall but falls and Ema saves her and compliments her for being brave.
The Academy police arrive to arrest Hikari for trying to escape but Ema uses his Sound Pheromone Alice on them to make them pass out, and Hikari nearly faints. Ema explains the ability of his Alice to Hikari. More people show up and Hikari escapes with Ema, who takes her to the Alice Grand Theatre, where the popular troupe, Baragumi, is performing. Ema gives Hikari a ticket so she can see him act in stage as an apology for the trouble earlier. Afterwards, Hikari compliments Ema for his singing but is surprised when he says he won't join the Troupe because he doesn't want to rely on his Alice to act, and he proceeds to sing to her. The effects of his Alice almost force Hikari to kiss him but she manages to resist when his song ends. Ema asks Hikari to be his "little sister" so they can work together as an Alice and non-Alice. She accepts.
Shortly after, Hikari is cleaning the classroom and cheers for another girl. Mikan Sakura and Natsume Hyuga visit the music school and stop by Hikari's classroom to see Aoi. Hikari talks with Narumi about how she is not being sincere with her emotions when she acts and she needs to practice with emotions she is not good at. Natsume interrupts them, telling Hikari she is not suited for acting and its best she quit. Mikan realizes Hikari is Tsubasa's sister and tells her that Tsubasa is her senpai, and Hikari is excited that Mikan might know where Tsubasa is. Natsume gives her a message Tsubasa sent for her: quit the music school and don't get involved with Ema. Hikari is shocked that Tsubasa not only knows she is in the school but he wants her to quit.