Namekuji (or Forest Ghost) are some NPCs that are drooling, slug-like creatures whose essence 'sticks' to Madotsuki when she touches them in the Forest World. There are two types of them: the first type has a pink outline, with white eyelids while vomiting maroon liquid, the second type has a purple outline, yellow eyelashes while vomiting green liquid. There are, in total, 12 Namekujis in the Forest World, with 6 of each type.
Interaction
Interacting with them directly will show their wiggling shadow stick on Madotsuki's head (or being possessed), their shadow will follow Madotsuki anywhere in the Forest World unless she goes to another map.
They don't react with any of the effects because they are a part of the chipset background of the Forest World.