Photos of Keisuke Honda's winning goal were splashed across front and back pages of the country's newspapers while TV and radio talk shows were buzzing about Japan's first World Cup win on foreign soil.
"Honda's Victory Bullet," screamed the Sankei Sports while the Nikkan Sports went minimalist under the headline "Honda!" in huge blue Chinese characters.
Several newspapers carried pictures of Honda, arms in the air, being carried on the shoulders of his joyous team mates as if Takeshi Okada's side had won the World Cup itself.
Cutting a slightly forlorn figure at the back trying to get closer to Japan's new golden boy is the team's most-recognisable figure, Shunsuke Nakamura, recently relegated to the bench.
"The key players were Honda and (Daisuke) Matsui," former Japan coach Philippe Troussier told Reuters, pointing out the two players involved in Japan's 39th-minute winner.
"Matsui with his great experience in Europe and Honda with his Champions League experience had a strong impact. No one took Japan seriously.
"The Cameroon players seemed so arrogant...seemed to take the Japanese as a weak team."
"Three points is not enough for qualification," added the Frenchman, who led Japan to the last 16 as 2002 co-hosts. "The (third group) match against Denmark will be a final."
OH NO! TULIO!
Japan fans decked out in blue watched their team's Group E opener in high spirits, some faking terror every time centre-back Tulio touched the ball after two recent own goals.
"Oh no! Tulio!" shrieked 23-year-old florist Miki Sato as she nursed a vodka and tonic during the match, which finished shortly before 1 a.m. local time. "Keep Tulio away from the ball!"
However, the big Brazilian-born defender, who scored own goals in Japan's warm-up losses to England and Ivory Coast, won media praise for shackling Cameroon captain Samuel Eto'o.
Even Japan's conservative broadsheet press appeared to have caught World Cup fever.
The Asahi newspaper carried the headline "Door to a New Era" while the Mainichi perhaps got a little too carried away, calling Japan's upset an "Easy Win" across the top of its sports page.
"It's so cool," said 41-year-old bar owner Eiji Takahashi after kicking out the last of the revellers as the sun began to rise over Tokyo's trendy Shibuya district.
"I thought Japan were complete duffers. It wasn't a great game but at least we've won a game. Maybe we can do a number on Holland in the next game!"
