Land of the Lustrous by Ichikawa Haruko (Japanese: Hōseki no Kuni, lit. “Country of Jewels”) is an ongoing manga series. It has been serialized in Kodansha’s Monthly Afternoon magazine since October 25, 2012; there have been ten collected volumes thus far. Volume One collects the first six issues.
Six times meteors smashed the Earth. Most land was battered and submerged. Humans as we know them are long extinct.
Humanity does have descendants. Of a sort.