"I only understood how hard these years were for her when I grew up, moved to Tokyo and graduated from Waseda University," he adds.

In those hard days, nature was the child's faithful playmate. It provided the venue, tools, and also occasions for joy, and somehow transformed their bitter lives into the beautiful "good old days".

For his son, the illustrator, who was born in Tokyo, these memories meant little as there was no family album to help retrieve them. For this work, he had to return to his father's hometown on several occasions to search through the local archives to discover facts and find inspiration.

"His poetic stories tell me that besides games and TV, nature is also a form of entertainment, which I think is especially valuable to young people living in the 'concrete jungle'," Shinji Ide says.

"Besides, winter is not always as cold as you expect and there is a strong festive mood in those dark months (in big cities like Tokyo). But I never really understood my father's longing for spring back then," he adds.

As the chairman of the Japanese Society for Rights of Authors, Composers and Publishers, the father has visited China many times since 1983, and has written two songs on Chinese themes.

The original Japanese song on which the book is based has several versions in different Chinese dialects.

According to a 2014 article by Lyu Yuan, the translator behind the first Chinese version, the song was so familiar among Chinese audiences that people believed it was an original Chinese work.