Yuuki Yuuna wa Yuusha de Aru

The story takes place in the era of the gods, year 300. Yuuna Yuuki lives an ordinary life as a second year middle school student, but she's also a member of the "Hero Club," where club activities involve dealing with a mysterious being called "Vertex."

[From Myanimelist]

This game was released with the first DVD and Blu-ray Disc volume for the anime. This is a short, fan disc-like game that takes place during approximately the first half of the anime. It contains ten short scenarios.