The joke is that these characters are trapped in a mobile game and spend every episode trying to convince people to download it, treating marketing desperation like an actual survival mission. The show treats its own existence as a joke you're allowed to be in on. It's comedy built from the contradiction between what they're doing (promoting a smartphone game) and how seriously the show treats it (like it matters).

Kureha and the other members of the Defense Squad live in the Irodori Settlement, in a world whose people stay cheerful despite its harsh landscapes. They spend their days holding meetings about how to attract more players to Hagane Orchestra, the smartphone game they appear in, and they are willing to try anything to promote it. Nothing is off limits, from the game's behind-the-scenes story and inner workings to friendship, determination, betrayal and despair. A young man tells his story alongside the girls, his friends and the Haganes, all pulling together like the players of an orchestra. The episodes are short, and the tone is comedic adventure.