The audition was announced on 5/29 on S/milage's official website, as well as Tsunku's twitter account.
Tsunku posted to his official twitter, saying "From the very beginning I stated that the number of members was not fixed. I'm just now putting that into practice. Sorry to trouble you."
Applicants must be middle or high school girls, or girls within that age range. The first round of interviews will be held June 4th at TKP Shibuya Conference Center in Tokyo and will continue throughout the month. The website states that auditioners will be able to participate in Morning Musume's 10th generation audition as well, but will only be able to enter one group should they happen to pass both.
Upon S/mileage's debut, there was much uncertainty as to whether all four girls would make it into the group - now there only remains to see how many new members will be added!