50 idols of Horipro (big entertainment production), including Itano Tomomi (AKB48), Yazawa Erika (Idoling!!!), and Adachi Rika, will show up at the fan event, “Summer Party-Horipro 50th Year Anniversary! 50 Idols Assembly“, on the 24th.
At the event, they will play games, have quizzes, give music performances, and more. The event will be broadcasted live on Niconico Douga at 14:30 (day time event), and also at 18:30 (night time event) in Japan.
source
: TOKYOHIVE