"Festivals" are just like that, often possessing a special magic that makes people do things they usually wouldn't do, wear clothes they typically wouldn't wear.
Qi Yi, who was adept at solving problems, naturally thought of the solution to wear the clothes Yan Yan had given him before.
Even Qi Yi wasn't quite sure why he brought this particular piece of clothing to Melbourne, but in the end, he stuffed it into his suitcase at the last moment.
For Qi Yi, he might have simply thought that he should carry with him the first gift his girlfriend gave him after their reunion.
Qi Yi surely never expected that he would actually wear such clothing out in public when he brought it to Melbourne.