A social game called The Magical Girl Raising Project allows one in tens of thousands of people to be a "magical girl" — possessing extraordinary physical capabilities and looks, as well as special magical powers that set them apart from the rest of the human race. But one day, in a district containing 16 magical girls, the administration announces that it must halve the number of magical girls to solve the problem of magical energy.
(Source: Anime News Network)
— Description from AniList community (anilist.co).
