Can I buy ayu goods after the concert begun ?

[YJ...]

Can I buy ayu goods after the concert begun ?

Usually before the concert starts, there will be many ppl lining up outside the stadium to buy the goods, right ?

Coz im planning to ask my fren in Japan, who is not an Ayu fan, to buy some goods for me. He is not going to line up whole day for me, so i juz wan to know if they are still selling the goods after the concert begun.
If yes, then after the concert begun my fren can juz drop over n buy it without much hassle.

Thanks.