Herge at his desk in his studio. [Photo/Agencies]

"I owe Chang a better understanding of friendship, a regard for poetry, respect for nature ... He was an exceptional person," Remi said in his biography. "He led me to discover and appreciate Chinese poetry and Chinese calligraphy 'wind and bone', the wind of inspiration and the bone of confident draughtsmanship."

Chang had returned to China before The Blue Lotus was published in 1936 and lost contact with Remi during World War II and after.

In the first letter to Chang in 1975 after they resumed communication, Remi thanked his friend "not only for the assistance that you brought me at that time in my work, but also for the knowledge you brought me."

"Thanks to you, my life took a new orientation ... You made me discover the qualities of things, poetry, the feeling of the unity of man and universe," he added.

In 1981, Remi and Chang, a successful artist and sculptor, finally reunited in Brussels after 46 years. Their meeting was broadcasted on Belgian national TV, drawing millions of viewers from around the globe.

Remi died in 1983. Fifteen years later, Chang also passed away. But their friendship endures in the hearts of Tintin's readers in both China and Belgium.

In 2015, China opened a culture center in Brussels and held a special exhibition on Chang's artworks and connection with Remi.

Tintin has become a national treasure for Belgium, just like the panda is one of China's. In February 2016, a panda cub was named "Dingding" in southwest China's southwestern Chongqing Municipality in honor of China's friendship with Belgium.