Aoyama is a serious 10-year-old boy who records all of his day-to-day experiences in his notebook. One day in May, penguins inexplicably appear in his home town, despite being located a long way from the sea. When Aoyama sees Big Sis a young woman who works at a dentist s office drop a soft drink can which inexplicably turns into a penguin, he decides to investigate and resolve the mystery behind these strange events.

Together with his classmates, Aoyama happens upon a strange phenomenon which is surely the key to these goings-on. Will their investigation bear fruit, and just how is Big Sis linked to these occurrences?

Contains the film on DVD with both the English dub and the original Japanese track with English subtitles