TEAM MESSAGE is the clothing brand that Ayu collaborates with for her apparel nowadays. Their name is on the clothes, but their logo is changed on Ayu's own tour merchandise to fit her tours. Previously, ASHxDIAMONDS, PUMA, and MTRLG along with other designers handled the apparel, but since around 2005-2006, Ayu has strictly used TEAM MESSAGE, except like in the case of a-nation '06.
If you glance at their site, you'll see that many of their designs are the very ones used during the Ayu concerts [specifically CDL05-06 and AT06.]