Fourth season of Strike the Blood.

Operation Victory Arrow is set in the period between the end of Operation Mars in the second television series and the 2012 Strike Witches movie. The three 30-minute short stories depict the lives of the members who returned to their respective homes. (Source: ANN)

While several of the girls investigate Vatlers ship afloat, Akatsuki and Himeragi wake up alone in the school gym with no memories of the day before and no explanation for why they were asleep on the same futon and why Himeragi is wearing an old-fashioned school PE uniform with bloomers. A bloody baseball bat and missing weapon soon deepen the mystery as assorted forces race to solve the mystery of the empty boat, the bloody bat, and the purple bra in the MCs pockets!

Yoshika Miyafuji joins the 501st Joint Fighter Wing, a defense unit specializing in taking down alien beings known as the Neuroi. However, in days of no invasion, she and the members of the unit are taking down day to day tasks like cooking and laundry. (Source: MAL News)