(http://www.chage-aska.net/en/information/1455)
We regret to inform you that CHAGE and ASKA’s [Special Live 2013, “On Your Mark”], performance scheduled for August 28, 29 and 31 at the First Gymnasium of Yoyogi National Gymnasium will be postponed for the following reason:
For some weeks, ASKA had been complaining of ill health and has received detailed examination by physicians. As a result, transient cerebral ischemia has been suspected and although the symptoms are not critical, the physicians have diagnosed that the symptoms require further follow-up and treatment and rest is necessary. Although ASKA has expressed his strong wish to appear on stage in August, the related parties have deliberated this matter and have come to the conclusion to postpone the special live this time.
CHAGE and ASKA wishes to express their deepest regret to the fans that have been waiting patiently for the first live stage to take place in six years and also of the concern this news will bring to their fans.
ASKA is now concentrating on receiving treatment in order to realize a fully prepared concert of CHAGE and ASKA. We ask for your understanding and request you to provide a gentle watch over the situation
Japanese Source:

http://www.sponichi.co.jp/entertainment/news/2013/06/11/jpeg/G20130611005992020_view.jpg