Start as a Parasite

Jiang Gan died, and Jiang Gan turned into a parasitic louse. Entering the host's brain, Jiang Gan took control of the host. This is a space where cold weapons and mechas coexist, but the host controlled by Jiang Gan is still in the Neolithic Age of primitive people. Facing the advanced civilization of the outside world, how should Jiang Gan survive?