If Japan Wins

There was a football match between Germany and Japan last night. I was convinced that the German team was powerful, and I didn't expect Japan to win. The match was held at midnight in Australia, so I didn't watch the live broadcast and went to bed.

However, I saw the news that Japan won the much this morning. It was surprising. The Japanese team defeated the German team.
It wasn't only me. Many Japanese believed that Japan would lose.

Then, there were some exciting things that happened.
Before the match began, many Japanese declared on Twitter, "If Japan wins, I will do XXX."
One guy said, " If Japan wins, I will ride from Yamaguchi to Tokyo by bicycle." The distance between Yamaguchi and Tokyo is about 1,000km. He regrets what he just tweeted.
The other guy said he would change his hairstyle to a strange design. This isn't a bad declaration. He can cut his hair short if he doesn't want to keep it.

Here is the terrible one. There were guys who said that they would run in a town naked. The same declarations were seen here and there. They probably chose the most embarrassing thing and hesitated to act because they didn't think Japan would win at all.

Well, what are they going to do?