Ubusuna (産土蟲, lit. Home Protecting Mushi) are mushi that live in the native plants and soil. Ubusuna are attracted to the scent of their homeland. They dwell mostly in the plant life of that region.When a child eats those particular plants then that child becomes host for the Ubusuna as well. If these children don't get enough food with Ubusuna in it the child may develop slow.
These mushi aren't very powerful, if the host leaves the native region they loose their power completely, but when the host returns to the region the Ubusuna's power returns and they protect the host from minor Mushi.
Mud like appearance of Ubusuna
When in the ground the mushi resembles mud, and above the ground it takes the appearance of smoke.