Mameo is a young kid that goes to the same school as Netto and his friends, and is in the same grade as Chisao. Mameo utterly hates vegetables with a passion, to the point that even smelling them makes him feel sick.
Mameo's desire to rid every bite of his food from all vegetables leads Slur directly to him. She offers the gift of Asteroid Plantman, who grants Mameo's wish of vegetable freedom. However, the evil navi goes beyond Mameo's control, and eventually turns on him. Enzan and Netto are forced to stop Plantman (deleting him once again), and Mameo learns that he actually LIKES vegetable after he has to eat his way out of a cage made of them.
After this certain episode, Mameo has yet to show up again. Can't say I'll miss the annoying little fellow.