These other Japanese fans were also Yuzuru fans, I assume, as you have brought this story a couple of times already before and you have mentioned this detail then
It is not about Yuzuru fans as such, it is about people coming to see a great star, and Yuzuru is just the greatest star of this sport.
I was to the Warsaw Cup once where Jason was the star. A big number of people arrived just for penultimate group to see him skating in the last group. They were not interested in anyone else, just wanted to see the great Jason Brown. They were made to wait until a break between groups and asked to take a seat without making too much fuss. Otherwise, no one was making a big deal about it. Volunteers were sent to distribute coffee and tea among the crowd until they were allowed to enter. After the skate, almost everyone was queueing for Jason's autograph, which lasted well into the Pairs event leaving most of the seats empty for them while Jason was giving autographs in the top corridor and talked to fans.
Shall we now pick up on Jason fans and Jason himself, lol?
You see, this is all on organizers.
In tennis, they just shut the door during games, and open them for breaks only. Nobody cares if seats are left empty when paid for, they care only for seats unsold (which I guess is true for any event organizers, really). Especially when it all lasts for so many hours, everyone needs to be cut some slack. They just make sure people don't disturb the players and the games by coming in and out and moving around when the game is on. If they do, they are called out by the umpire and asked to take a seat. The game does not start until they do. Otherwise, no one cares.
I also guess people are much less disturbed by this moving around when they actually do like the skater these unorderly crowds arrived for so they are kind of sympathetic to their cause. When you do not like the skater it all is happening for, I guess you get double disturbed and ready to complain.