On September 9th, the day of the Katakai Fireworks Festival, high school student Hana comes home from the hospital after six months of treatment for leukemia. She then discovers that her older brother Taro has become a social recluse. Taro used to be tender, smart and proud of his younger sister, but now he even turns his back on her and stays in his room. With Hana's help Taro slowly opens up to the world again. Then, with winter approaching, Hana has a relapse with her leukemia. Taro comes to the hospital everyday to visit Hana and soon learns that the Katakai Fireworks Festival is a symbol of happiness for Hana. Taro then takes the initiative to make Hana happy and approaches the town's youth group once more for admittance.
Natsuki Kashiwagi es una joven que, tras la pérdida de sus padres en un accidente, vive con su hermano autista Daiki. Un día vuelve a aparecer en su vida Sōta Funahiki, un amigo de la infancia que se había marchado a Canadá. Antes de su partida, Sōta le había dejado a Natsuki un anillo de compromiso, prometiéndole regresar para darle otro, pero habían perdido el contacto. Natsuki y Sōta comienzan a salir de nuevo, haciendo que Natsuki recupere su sonrisa.
