Asumi, a depressed and bored bookstore employee, is killed by a burglar on his way home from work. He wakes up in a strange world where he has become a beetle with a mysterious evolution system. The system allows him to gain new abilities and forms by consuming other creatures, but also puts him in constant danger from predators and enemies. Asumi embarks on a perilous journey to survive and evolve, hoping to enjoy this new life and find a way to get back home. Along the way, he encounters allies and foes, challenges and opportunities, and discovers secrets about this new world.