Land of the Lustrous

Many moons ago, Earth was pelted by six meteorites resulting in the creation of six moons, and only one island remained. Those who were unable to reach the island sunk to the ocean floor, where they gradually transformed into crystals over countless ages. Twenty-eight of these crystallized beings, known as the Lustrous, materialized from the depths and established a dwelling on the island. Guided by the wise Kongou-sensei, they were obligated to protect themselves from the infinite number of Lunarians residing on the moons, with the intention of harvesting their precious bodies to craft jewelry and weapons.
The story revolves around Phosphophyllite, a young gem on the verge of turning three hundred years old. They’re awkward, incredibly frail, and seem to have no discernible abilities, making them one of the weakest gems in existence. As their struggle against the otherworldly invaders intensifies, they learn that every power has a price, and no one should have to pay such a cost.