I found several maps for Tokyo:
Harajuku (takeshita dori): the ticket reseller shop is called "Gorakudoh"

more info:
http://haropedia.mrwaffle.org/wiki/Gorakudoh
Shinjuku: ticket reseller shop is called "tizu" or "yokohamaticket" (?)
Shibuya: ticket reseller shop is called "tizu" or "yokohamaticket" (?)
Ueno: ticket reseller shop is called "tizu" or "yokohamaticket" (?)
BTW, anyone knows what area should to look to buy GOOD SEATS for Saitama Super Arena concerts? (level 200 = arena seats on Block B~C?)
thank you so much in advance !!
I'll be arriving Tokyo in April 1st and I'm staying close to Ueno station ^^