Twin giant panda cubs Xiao Xiao and Lei Lei, born at Tokyo's Ueno Zoo, turned 2 years old on Friday.
Many fans flocked to the zoo in Taito Ward even before opening time to celebrate the twin cubs' birthday.
Since March, Xiao Xiao and Lei Lei have been living away from their mother, Shin Shin. On Friday, visitors took pictures of the twin cubs and cheered as the two played together and shared a bamboo stick.
Seiko Mizobuchi, a 53-year-old housewife from Tokyo's Setagaya Ward, said: "I was happy to see them stick together. I want to continue to see them."
Naoya Ohashi, chief of the zoo's education division, said that he feels "grateful as (the cubs) have grown without problems."
"I want them to continue to grow and contribute to panda preservation," he also said.
An event to create congratulatory message cards for the twin cubs will be held at the zoo until Sunday. Photo panels showing their growth will be exhibited at the zoo until August.