The protagonist is an ordinary soldier from an empire at war who is used as a guinea pig for genetic engineering experiments. Transformed into a monstrous creature, he is placed into cryosleep. Two hundred years later, he awakens inside an imperial research facility as a calamity-class enhanced monster. The empire that created him has long since collapsed, and he now finds himself in a world of swords and sorcery where monsters are killed on sight.

Inside this monstrous body resides the soul of the former soldier, Eunos. Horrified by his own appearance, he despairs, believing that anyone who sees him will immediately try to kill him. Despite this, he resolves to find a way to coexist with humanity. Using his incredible physical abilities, which include enhanced vision and invisibility, he begins defeating vicious monsters and saving humans in need. He encounters various people, including women and elves, who require rescue.

A major obstacle prevents Eunos from achieving his goal of peaceful coexistence: he cannot speak the language of present-day humans and can only growl. This communication barrier makes him unable to explain his intentions, leading the military to mistake him for a hostile target. He is thus forced to survive alone in his monster form while continuously being hunted.

The story follows his survival fantasy journey as this lonely, super-strong monster attempts to live a peaceful slow life despite being a target of the military and a world that fears him. The narrative focuses on his experiences of exploration, combat, and encountering new situations without the typical character dynamics that spoken communication would allow. The manga is published by TO BOOKS, Inc and began serialization in 2021. Volume 1 was released in Japan on February 15, 2022, followed by Volume 2 on December 14, 2024, and Volume 3 on August 15, 2025.