Houseki no Kuni

In the distant future, a new immortal and genderless life form called Gems populate the Earth. The 28 Gems must fight against the Moon Dwellers, who attack them regularly to abduct them and to turn them into decorations. Each Gem is assigned a role, such as a fighter or a medic.
Being only 300 years old, Phosphophyllite is the youngest of the Gems and has no assignment yet. Phos wants to help fight the Moon Dwellers, but is too weak and brittle for battle. One day the master of Gems, Adamantine, assigns Phos the task of creating a natural history encyclopedia.

Note: Nominated for the 8th Manga Taisho in 2015.