When Norbert Egger and his wife planted a sapling during the foundation-laying ceremony for Rhein Chemie in Qingdao, Shandong province in 1995, they likely never imagined it would grow into a towering "tree of friendship" – a living symbol of the bond between their hometown of Mannheim, Germany, and the Chinese coastal city which Egger views as his second hometown.

At the time, Egger served as first deputy mayor of Mannheim. By 2015, that early gesture of friendship had blossomed into something greater - on the football fields of Mannheim, young athletes from both cities ran side by side.

"Amid sweat and laughter, friendship quietly took root," said Egger, now 86, during the opening ceremony of the 2025 Shandong International Friendship Cities Cooperation and Exchange Week held in Jinan, capital city of Shandong, on Tuesday.

"Today, this football event has become the largest youth exchange program between our two nations," said Egger.

"Sister-city ties are never just about formal agreements. They thrive on the bonds built over time, piece by piece," he said.