I'll be there on either the 9th or 10th May, but I guess Hatix already knows that

Perfume the other day.
Last year I got my ticket from Yokohama Ticket is Shibuya. Man, that place is hard to find though, had to get one of the locals to walk me to it
Can't remember exactly, but it was about 10-15,000 for a decent seat in the b-block.
Close enough for Ayu to give me a funny look halfway through the concert