This time, though, he welcomes it. Today, when he trots out at Twickenham, he will become the first Japanese to appear for Cambridge University in the annual Varsity Match.
"When the captain, Angus Innes, knocked on my door at College and told me I was selected for the Varsity Match I was very excited, possibly more than I had been for the World Cup.
"There will be more than 60,000 people there. The biggest crowd I have played in front of is 40,000 in the Hong Kong Sevens last year when Japan beat Scotland in the Plate final."
Iwabuchi is not the first Japanese to appear in the traditional fixture. Oxford have fielded two, the first was the prop Toshiyuki Hayashi in 1990, the other was back row forward Takuro Miuchi last year. But Iwabuchi is well aware of the special place he will hold in Varsity history and it has certainly helped to offset the misery of Japan's World Cup.
"I had been really looking forward to getting on during the World Cup," said Iwabuchi, "although realistically, because of the strategy Japan has adopted, I knew I did not have that much of a chance, so although I was disappointed it was not totally unexpected.
"But as a squad we had really believed we could progress at least to the second round stage of the tournament so, after losing the opening match against Samoa very heavily and then the remaining two, we were very down."
Iwabuchi is in the second of a two-year course studying social and political sciences, having first obtained a degree at Aogakuin University in Tokyo in International Politics.
The 23-year-old Iwabuchi does not harbour any ambitions to enter mainstream politics, however. His sights are trained more obliquely. "I might run my own business," he mused, "but I also want to study for an MBA, maybe at Harvard in the United States.
"But international politics interests me as well and I might see if a body such as the United Nations would have something for me. There is not a Japanese on the UN committee, so maybe I could be the first of my country on that, although I would have to improve my English."
Before all that, though, he has two more immediate goals. "One is to play professional rugby in England and the second is to study for a PhD in Political Science or Political Thought."
He is realistic about his chances of playing professional club rugby in England, though. "The main problem is that I am Japanese and do not have a British or a European passport," he said. "And because only two foreigners are allowed to play for a club at the same time most of the teams would look to South Africans, or big players from other countries. I am a fly-half and not big enough."
In their build-up to today Cambridge have played a number of club sides including Leicester and Northampton, but Iwabuchi's mail pigeon-hole has remained empty.
"When we have played clubs this season I have tried to impress them. Unfortunately they have not made contact with me." Amid the stoicism, though, lurks a steely pride, "I have not written or telephoned them," he added, "but this is my big match. It is very important for me to show what I can do at Twickenham." With his pace and thoughtful approach, that should be plenty. Oxford have been warned.Reuse content