Aji, an orphaned boy, watches as other children celebrate their birthdays with balloons and the cheerful song “Happy Birthday.” The simple sight awakens a longing to experience the same joy for himself. Using money meant for his daily necessities, Aji secretly buys a balloon. But before he can celebrate his birthday, the balloon deflates. While searching for a replacement, Aji discovers an unfamiliar object that resembles a balloon. Unaware of its true purpose, he blows it up and uses it to celebrate his birthday alone.