After catching the girls snooping at her room while Ichika is massaging her, Chifuyu has a talk with the girls about their feelings for her brother and gives them some advice. The next day, Houki's eccentric sister Tabane arrives to deliver Houki's personal IS, the Akatsubaki, a 4th generation IS with abilities far more advanced than the others. However, Chifuyu soon receives news that an an unmanned US/Israeli IS called the Silver Gospel has gone out of control. After assessing the situation, Chifuyu orders Ichika and the girls to stop it while Ichika and Houki will pursue it as only their IS are fast enough to catch up with the Silver Gospel.