He says he saw cats at modern convenience stores such as 7-Eleven as well, but he chose to focus only on cats in settings with an olden-day charm.

"It's a tradition to raise cats in grocery shops to keep away the rats in Hong Kong," says a 60-year-old male resident of the city whose surname is Ho.

A friend of Heijnen, who's not willing to reveal her name, says: "The streets in Hong Kong are so crowded and noisy, but the cats look so peaceful and beautiful in his photos."

Heijnen says many local residents have told him that they saw what he saw every day, but they didn't realize that "anybody could do something so beautiful" with such views.

Heijnen feels the same about his hometown, Amsterdam, where he wouldn't pick up his camera to shoot daily life. "Too familiar," he says.

Hong Kong, on the other hand, has offered him a totally different culture.

He recently asked his local friend, Aki Leung, to give him a Chinese name after he decided to publish his third book. But he still finds the name, Ma Yixiu, a bit difficult to pronounce.

Heijnen is studying Chinese at a Hong Kong language school, and uses an app to practice daily.