Click to enlarge it.
Apparently, Sakai Yui is a big fan of CLAMP and she used to go to the same Manual Therapy Center as CLAMP, they got to know each other through a mutual doctor from the clinic.
Sakai Yui talks about the illustration in her official blog.
You can check CLAMP's messages of support in the Message section of CLAMP-NET.COM.
This is so cool! I thought it looked very much like her =D And that was a very nice gesture of CLAMP!