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, seu irmão Daiki e Souta são amigos de infância. Ainda pequenos, Souta se muda para o Canadá, deixando Natsuki com um anel de ‘noivado’ e a promessa de voltaria para lhe dar outro anel, mas eles acabam não tendo mais contato por muito tempo. Os anos se passam e Souta volta para o Japão, reencontrando Natsuki algum tempo depois, na véspera de Natal. Natsuki e Souta logo começam a sair juntos, mas infelizmente, ele sofre de uma doença grave.
