You already have a name, and a clock

You are Takumi Sumino. Face and a few starting habits are yours; the plot is not a custom Origin you can swap. The collected first-scenario page starts as an ordinary life in the Tokyo Residential Complex — school, a childhood friend the collected Karua Kashimiya page names as classmate and breakfast guest, a morning that still thinks it is normal. Then the street is not. The job is to keep Last Defense Academy standing for one hundred days. This is a story with battles in it, not a campaign you can min-max on day one. This room will not name where she went after the siren, or what a later chapter does with that name.

Heads up. People boot this expecting a clean SRPG campaign and then ask why a morning conversation just closed a route.