Newspaper headlines boasted of "history in the making" after Japan reached the last 16 of the World Cup for the second time, while television viewing figures nudged past 41 per cent despite the game finishing just before 5:30 am local time.
The famous "scramble crossing" intersection in Tokyo's Shibuya district erupted in a crescendo of chanting and drumming as more than 1,000 fans celebrated the victory.
"I'm still shaking, I just can't believe it," tearful 21-year-old Yuka Higashi told Reuters. "Honda's amazing!"
Midfielder Keisuke Honda scored Japan's first goal against Denmark in Rustenburg after firing the winner against Cameroonin their opening game.
Japanese Prime Minister Naoto Kan, on official business in Canada, sent a message of congratulations to Japan, who arrived at the tournament in a miserable run of form but now face Paraguay on Tuesday for a place in the quarter-finals.
"I wish to congratulate the team on their excellent achievement," Kan said. "The side has given the whole country energy and pride."
Energy drinks were being guzzled by many fans as euphoria gave way to exhaustion and thoughts of a train straight to work.
"I won't get any sleep now," said 33-year-old banker Tsuyoshi Hamada. "Shower and straight to the office. It's worth it though."
In Osaka, more than 50 fans plunged into the murky waters of the city's Dotonbori river in a repeat of the jubilant scenes of 2002 when Japan reached the last 16 as World Cup co-hosts.
Former Japan captain Hidetoshi Nakata also added his support.
"That's the sort of game we've wanted to see," he said. "They've grown up at this World Cup. Now let's hope they can go further than we did in 2002."