Higher Tribe: Ichiban no Sanmyaku

Hokkaido is an island of extreme cold. There, scientists and members of the Japanese self-defence force investigate a mysterious animal attack, and discover a frozen mummy in a cave. When they return from the cave, one of the investigators undergoes a strange metamorphosis – a new organism emerges from the destruction of the human body. Mankind has encountered the "Higher Tribe" and falls into despair.

(Source: LINE Manga, translated)