Washio Sumi wa Yuusha de Aru

Three elementary school girls—Sumi Washio, Sonoko Nogi, and Gin Minowa—are assigned a crucial mission in the year 298 of the god era. They must take on the role of heroes to confront Vertex, an enigmatic threat attacking Shinju-sama, the god tree safeguarding Shikoku, the last livable region on Earth. Unbeknownst to them, their battle will demand a greater sacrifice than they anticipate. This is the first manga adaptation of the series, which was later cancelled.