淘气的张韩一（朴智彬 饰）是一名九岁的孩子，经常逃课或在学校捣乱。十二岁的哥哥韩星（崔佑赫 饰）则是个懂事乖巧的孩子，对弟弟照顾有加。虽然性格各有不同，两兄弟依然相亲相爱。

Nine-year-old Hani is a troublemaker who isn't afraid of anything. A precocious punk, his school friends are all his underlings, and even his family members are under his control. He especially considers his elder brother, HanByul, who often complains of being sick, his greatest target. Until one fateful day, HanByul collapses at home and is rushed to the emergency room and the worst nightmare for any parents becomes a reality - he is diagnosed with cancer. The film is based on a true story.

말썽꾸러기 아홉 살 한이는 아프다고 투정부리는 형 한별을 자주 괴롭힌다. 그런데 어느 날 한별이 쓰러지고 한이는 형의 머릿속에 종양이 있어 잘라내야 한다는 소식을 듣는다.

Han-yi es un niño de 9 años, no trata con mucho respeto a su hermano mayor Han-byul de 12, a quien molesta permanentemente con bromas. De pronto, a Han-byul le diagnostican un tumor cerebral y es sometido a una operación. La historia está basada en personajes reales.