A poor girl rescued a little bird from a spider's web. The bird stayed with her, and they lived happily together. Wherever the bird might be, it would fly back when the girl whistled, and sing a beautiful song for her. One day, the girl won first prize at a "Bird Calling Competition" held in a park, and was given the job of taking care of the "Bird World" in the park. She was so fascinated by the many beautiful birds she had never seen before that she forgot about her dear little bird. Forgotten by the girl and made fun of by the beautiful birds, the little bird flew away. The girl, however, did not notice that her little friend was gone. She continued taking care of the birds, but then she became ill and unable even to whistle. At last, she remembered the little bird, her real friend...
This story has an atmosphere, which is slightly reminiscent of the famous children's story "The Happy Prince". The beautiful friendship between a poor girl and a little bird, man's foolishness to become easily fascinated by pretty or new things only to lose something very important, and finally the importance of the faith you can put in somebody even if you are betrayed and hurt. With these elements, Tezuka Osamu unfolds his story to a tragic ending just like Andersen's (and the ending of "The Happy Prince").