Eternal Sonata features ten playable characters (listed below) as well as a group of colorful villains. All the characters are named after music-related terms, and some of their weapons even resemble musical instruments (such as Beat's gunhammer having the shaft of a clarinet).
Japanese Voice: Mitsuaki Madono
English Voice: Patrick Seitz
"Death is a reality that is far too real."
His full name is Fryderik Franciszek Chopin. Born in Poland in 1810, he is known as the "poet of the piano". Of weak constitution, he nevertheless has a deeply sensitive and subtle personality. In particular, the loss of his 14-year-old sister Emilia to tuberculosis left a deep scar on his heart. Chopin can see traces of her in Polka, also 14 and destined to die. While knowing that the world in which he meets Allegretto and Polka is just a dream he is having on his death bed, gradually he becomes more and more confused by how real the world feels. He begins to question where his true feelings lie. All the words he speaks come out as poetry.
Japanese Voice: Hiro Shimono
English Voice: Sam Regal
"It doesn't make sense! In this world the people with shining hearts are the ones who suffer! ...That's supposed to be okay?!?"
A boy who works as a bread thief in the port city of Ritardando to provide food for poor children. Though he knows what he is doing is wrong, his strong sense of justice refuses to let him abandon the children. He uses rough language and occasionally even hits his young friend Beat, but in reality he is deeply emotional, and thinks of his young friend as a little brother. With the contradiction of a world where the gap between rich and poor lying especially hard on his mind, Allegretto sets off on journey. He is captivated by Polka, who makes light of her own tragic fate while living each day with earnest, and resolves to save her.
Japanese Voice: Aya Hirano
English Voice: Erin Fitzgerald
"I want to use this limited life of mine to give everyone happiness."
A girl who lives with her mother in the village of Tenuto, on top of a hill overlooking the port of Ritardando. She makes her living by selling Floral Powder, extracted from Tenuto's unique flowers. However, due to the circulation of cheap government-recognized Mineral Powder, lately she has been unable to sell any medicine at all. In a world where magic is a side-effect seen in those cursed by a fatal and incurable disease, death is always close to a magic-user such as she. Added to such a cruel fate are rumors flying about that the disease is transmitted simply through contact, leading Polka to be shunned by humanity and causing her to lose all trust in others. However, after meeting Chopin, she decides to use what little remains of her life to help others.
Weapon: Clarinet Gunhammer
Japanese Voice: Yumiko Kobayashi
English Voice: Mona Marshall
"Why is bread this expensive? If it were a little cheaper, we could just buy it..."
Works as a bread thief with Allegretto in the port city of Ritardando. Beat calls Allegretto "Niichan" (big brother) and adores him like an older brother. A camera that is the only surviving memento of his father is his treasure. Beat is short for his age and is bothered by his height. Sporting a bright and cheerful personality, he is able to talk to anyone and everyone freely. Though he does not usually think very hard, in many cases his sincere words come surprisingly close to the real truth.
Japanese Voice: Houko Kuwashima
English Voice: Megan Hollingshead
A young woman who lives in a house in the middle of Chorus Plains and spends her time tending her goats. Viola is always accompanied by her pet squirrel, Arco. She has an outgoing, cheerful personality and an independent spirit. An expert with the bow, Viola lives off of rabbits and other small animals. She prefers a quiet life in the countryside to the crowded and noisy cities.
Weapon: Sun Rings
Japanese Voice: Mika Kanai
A young girl who has grown up surrounded by nature in Agogo Village. Salsa is full of energy, extremely self-confident, and very opinionated. Because of this, she has rather antagonistic relationships with Beat and Viola. Salsa has a tendency to jump to conclusions that are completely incorrect. She often brings humor to serious situations, without being completely aware of it.
Weapon: Moon Rings
Japanese Voice: Chiwa Saito
Salsa's twin sister. March is an introspective and kind young girl with a great love of nature. She often worries about Salsa's aggressive attitude and behavior but still admires her. Unlike her sister, March is soft-spoken and calm; she can truly get along with anyone. March is also very mature for her age, so she is able to understand difficult concepts with surprising ease.
Japanese Voice: Jouji Nakata
English Voice: DC Douglas
The leader of an anti-government group called Andantino. Jazz has a serious and determined personality. These characteristics help him make clear decisions in any situation, which is why he is a good leader. Jazz's only weakness is the blind spot he tends to have in regards to the people who are closest to him.
Japanese Voice: Tomoe Hanba
English Voice: Julie Ann Taylor
A young woman who is a member of Andantino, and a childhood friend of Jazz. Falsetto has romantic feelings for Jazz but has never been able to summon the courage to tell him. In part because of this, she is very antagonistic towards Claves, and often speaks to her in a sarcastic tone.
Japanese Voice: Mie Sonozaki
English Voice: Tara Platt
A member of Andantino, who is also Jazz's lover. Claves is very dedicated, but often has trouble remembering complicated strategies. She knows that Falsetto doesn't like her. However, Claves is also jealous of Falsetto because of the longtime friendship she shares with Jazz.
The Count who oversees Forte. Count Waltz is responsible for the raise in taxes that has made life difficult for the citizens of Forte. He is very self-assured and power hungry. It is suspected that Count Waltz is preparing for a war with Baroque.
Japanese Voice: Minagawa Junko
English Voice: Liam O'Brien
Count Waltz's close advisor. Legato handles the everyday tasks involved with running Forte for Count Waltz. He is completely loyal to Count Waltz and obeys his every command.
English Voice: Jamieson Price
Weapon: Two Swords
A cold-hearted young woman who is working as a spy for Count Waltz. Rondo is an excellent fighter with finely honed battle skills. She is also an expert tracker and assassin.
English Voice: Nicole Karrer
English Voice: Johnny Yong Bosch
A sarcastic, clever and confident young man who is on a secret mission for Count Waltz. Fugue enjoys inflicting pain and will start fights with people just for the fun of it.
The Captain of the guard at Forte Castle, Tuba is also one of Count Waltz's minions. Not particularly bright, Tuba uses his strength and large size to intimidate people.
The prince of Baroque, and captain of his fleet ship. He is a man who seems easily toppled by others ideals, yet he is not easily deceived. He is engaged to a beautiful young lady, Serenade, though their marriage might bring peace or destruction.
English Voice: Cam Clarke