Japan team wave to their supporters after defeating Ireland 19-12. Photo: Jae C. Hong/AP Photo

TOKYO  Japanese rugby fans were still in disbelief on Sunday, a day after the Rugby World Cup host team beat champion contender Ireland in an electrifying upset.

Tournament captain Michael Leitch told a news conference that a crucial factor behind Saturday's victory was the team's confidence that it could win - something fans admitted they hadn't believed.

"I couldn't sleep last night," said Tokuo Ukai, a 55-year-old who works for an electronics parts maker, his voice still hoarse from intense cheering at the stadium.

"I did not think they were going to win. Tears rolled down my cheeks. I almost wet my pants," he said. "I want to tell the Japanese team that I'm sorry I didn't have faith in them."

The Brave Blossoms had never before beaten Ireland, a team who were ranked world number one just a few weeks ago.

"What's amazing was they played the game believing they will win, although people including me, did not really think they stood a chance," said 63-year-old retiree Tomoyoshi Ito.

University professor Shunichi Takekawa said he had just become a rugby fan.

"The form they showed in withstanding Ireland's fierce attack was impressive. I want them to make it to the finals." 

Reuters