The Butt Graduation Festival (尻卒祭, Shiri Sotsu-sai) is a large-scale tournament, dedicated as a tribute to important players. The event is very rare as it will only be held when a specific important player decides to retire.
Nagisa Ujibe's Butt Graduation Festival
Ikumi Yuzuki's Butt Graduation Festival
Main article: Ikumi Yuzuki's Butt Graduation Festival
When one of the Five Butts, Ikumi Yuzuki decides to retire, the same event is held with the prize of 1 billion yen. However, there is an exception, thus both S-Rank and A-Rank players are allowed to participate in this event.