A 14-year-old boy. Seita is responsible, mature, and tough. Since his dad is away fighting in the war, he is responsible for all the jobs his father would normally take, including caring for his younger sister, Setsuko. Seita's main fault is his pride, which can cause him to make wrong decisions.
A 4-year old girl. Setsuko completely adores her older brother Seita. She is innocent and cheerful, and at times naïve to the terrors of war around her.
Seita and Setsuko's mother is an ideal mother figure. She is loving to her children and seems to have a good control of things, even during the war. Her husband has gone off to fight in the war on the cruiser The Maya.
Seita and Setsuko's aunt is attached to her values, which include hard work and solemnity during wartime. She is very strict and gives people what she thinks they deserve. This causes her to often be cruel.
Seita and Setsuko's cousin is sympathetic and thoughtful, much more so than her mother. She helps Seita several times during the film.