Nagi Aiza

Nagi is stubborn and somewhat childish. She is also cunning, and hard-headed. Nagi maintains a realistic look in life and repeatedly testifies her hate for cliché. Because of her unerring piano skills, she is slightly arrogant and claims herself as the "Angel of Kurumi Junior High". Nagi also appears to have a distaste for anyone who refers to their superiors without the appropriate honorific, as shown when Miike did not refer to Kousei as his Sensei or Senpai, instead addressing him directly as "Arima". Nagi is often seen to have a brother-complex, seeming to be completely fixated on her brother Takeshi. She idolizes her brother, and says she's "constantly chasing after him, but he is always ahead of her". This complex has driven her to follow in his footsteps in order to get him to notice her and to also stop her brother's own fixation on Kousei. Nagi sets up a plan to sabotage Kousei, resulting in her being "knocked out", and Kousei having to bring her to Hiroko's house. She then proceeds to ask Hiroko to teach her. Hiroko labels it as rude to her current instructor. Yet Hiroko asks her to play something. Nagi shows she is a brilliant player, and Hiroko agrees to teach her. She then shifts the position to Kousei, much to Kousei's and Nagi’s dismay. Kousei corrects every aspect of Nagi's playing, which makes Nagi upset and retorts how he thinks he knows it all. In the later parts of the anime, Nagi warms up to Kousei, comforting and trying to make him smile while he was upset. Nagi holds deep respect for Kousei and admires him for his piano playing skills.

Nagi is characterised by her blond pigtails and golden brown eyes, often seen wearing her school uniform. She is described as very cute and pretty. In her early teens, she has yet to develop a woman's body and height. She establishes the cute little sister character in the story. Hiroko also commented that she looked a lot like her brother because of her hair. During her school performance, Nagi wore a formal green dress with a bow to tie it off in the back, and a black choker with a white flower around her neck. Her hair is worn in a high side ponytail.