Judging from photos taken pre-concert, it's never TOO many people, but it's good to get there probably like an hour early just so you make sure you get the things that tend to sell out within an hour.
https://www.instagram.com/evanbon1017/
This guy on Instagram really loves Ayu! Has some really expensive taste in clothes too... has A BEST t-shirt in one of his looks and replicated Ayu's Opening Ceremony look on Instagram!