Drawing the line on a promise kept

He didn't try to persuade people not to eat meat or vegetables at all, but opposed unnecessary killing or the casual picking of flowers.

"I'm very moved by the story behind the book, the relationship between Li and Feng. Li was Feng's art teacher when Feng was a teenager, but not for a long time. They were not of a similar age, but the cross-generational friendship lingered," says Xu.

"Moreover, the agreement Li made with Feng may just be a casual one, but Feng tried his best to stick to it. After Li's death, Feng was displaced during the war, and suffered a lot, but he never forgot the promise he made to Li," she adds.

According to Feng's daughter Feng Yiyin, the last 100 cartoons were supposed to be finished in 1979, but Feng Zikai died of cancer in 1975. The family found that he had already finished the last volume in 1973, six years early.

"He made the promise that, if he lived long enough, he would keep his word and complete the collection. Although he didn't live that long, he still fulfilled his promise," she wrote in a 2012 article about the collection.