Name: Yoisaki Kanade Gender: Female Age: 17 Nickname: K Height: 154cm Attends an online high school. She has pale skin, long silver hair, and light blue eyes. She is often called cute due to her small stature. She is the founder of the circle [25-ji, Nightcord de.] (often abbreviated as 'Niigo'). She handles composition with her genius musical sense. She has a warm, deeply caring, and understanding personality. After her mother passed away from illness, middle-school Kanade composed a song for her father, who seemed anxious. However, her father collapsed from the shock of realizing Kanade was more talented than he was. He remains hospitalized with memory loss. Kanade blames herself for his condition and has developed an obsession with creating songs that can 'save' someone. She encourages the mentally unstable Mafuyu, telling her, "I'll keep making songs until I save you," and continues to write music for that purpose.

Name: Asahina Mafuyu Gender: Female Age: 17 Nickname: Yuki Height: 162cm Attends Miyamasuzaka Girls' Academy. She has purple hair and purple-blue two-tone eyes, with her hair tied in a ponytail draped over her right shoulder. She is widely considered a beauty. She handles lyrics and arrangement for the circle (Niigo). Publicly, she is an honor student with high grades who is active in the archery club and student council. She has a reputation for being a kind person due to her considerate attitude. However, Mafuyu's true personality is cynical and pessimistic. While she acts like a 'good girl' at school, she shows an eerie, low-tension side when she is with circle members or alone. She has been in an unstable state, including a fragmented sense of self due to years of gaslighting by her mother, but she is gradually improving thanks to Kanade and the circle members. The Empty SEKAI was created from Mafuyu's heart.

Name: Shinonome Ena Gender: Female Age: 17 Nickname: Enanan Height: 158cm She has short, light grayish-brown hair and brownish-orange eyes. She is an official beauty. She is in charge of illustrations for the circle's music videos. She has strong pride and is the type to speak her mind without hesitation. She is a sharp-tongued critic and is good at persuading others. However, she isn't just prickly; she is a kind person who empathizes most when others are struggling and actively steps in to help. She has a younger brother, Shinonome Akito, who is one year younger. Akito shares Ena's personality traits, making him a tsundere; they aren't exactly close and bicker often, but they are siblings who occasionally rely on each other. Influenced by her father, who is a painter, she dreamed of becoming one herself, but her relationship with him soured after he told her, "You have no talent for painting." Because of this, she strives for her art to be recognized. She respects and likes Kanade, who acknowledged her work by saying, "Niigo needs Enanan's drawings." She has a hobby of posting selfies on social media and is very popular, receiving likes and comments almost instantly after posting.

Name: Akiyama Mizuki Gender: Male Age: 16 Nickname: Amia He has pink hair and eyes, with his hair tied in a side ponytail. His pink eyelashes are a distinctive feature. He is in charge of MV production for Niigo. He loves playing pranks but is also deeply considerate and perceptive, never crossing the line. Since childhood, he has loved cute things, influenced by his older sister, Akiyama Yuuki. He faced subtle bullying for being a boy who liked skirts and ribbons and lacked self-confidence, but thanks to Yuuki's encouragement, he began to live doing what he loves. He hid his secret from the circle members, fearing that revealing his gender would ruin their relationship, but eventually opened up to everyone, starting with Shinonome Ena.

Name: Hatsune Miku Gender: Female She is the sole permanent resident of the Empty SEKAI. She has silver twin-tails and teal-pink heterochromia. She is quiet, deeply considerate, and kind. She is a Virtual Singer. She does not exist in the real world, only within the 'SEKAI'. She can appear in the real world as a hologram through people's smartphones.