Colorless

An enormous solar flare caused the planet to lose all of its colors. Humans are deformed and declining in numbers. The key to reclaiming the old world lies within the power hidden in "color," and one "girl." Knowing that the few remnants of colors in the world yield a great power, Avidia, who is conducting research while protecting a girl named Chie, uses the colors to expand his own power, and throws himself in a battle against the Cult.

(Source: Leed-sha, translated)