A $35 afternoon tea set served at the British pavilion at the Osaka Expo has left Japanese social media aghast at its perfunctory paper cups, sending Britain's embassy into damage-control mode.

"We have improved our service after some feedback saying we have failed to live up to expectations," a British Embassy official in Tokyo said in a video posted to X on Thursday.

"Afternoon tea is an important part of our tradition that symbolizes British culture," she said in Japanese.

Earlier this week, a post deploring the overall quality of the pavilion's tea set — including "a tea bag stuck in a paper cup" — went viral on X.

Many Japanese users reacted with shock, expressing their perhaps misplaced faith in a quintessential British afternoon tea set.

The paper cups have since been replaced by ceramics, the embassy official clarified in the video.

She said she hoped visitors to the expo would "deepen their interest in the richness and profundity of our culture."

Online, reactions haven't been all sweet.

"As a Brit resident in Japan, it's embarrassing, and ¥5,000!," one X user commented on the embassy's video. Five thousand yen is around $35 at today's exchange rate.

"Japanese believe us Brits hold high standards when it comes to tea," the user said.

The tea debacle is not the only thing to go awry at this year's expo, held in Osaka until mid-October.

Last week part of a motor propeller fell off one of the several drone-like "flying cars" being demonstrated at the event, with no injuries reported, Japanese media said.

Self-driving shuttle bus services, with drivers on board to ensure safety, were also paused after one of them had what reports described as a minor collision with a wall.

The Expo phenomenon, which brought the Eiffel Tower to Paris, began with London's 1851 Crystal Palace exhibition and is held every five years.