We don't know very much about this guy other than he was trying to use Asteroid Napalmman to do his evil crimes for him. Unfortunately, Domon's PET gets obliterated during one such scheme, leaving Napalmman to fend on his own, stranded in the internet. By lucky chance Napalmman becomes involved with a good man by the name of Nenji, who takes care of him.

When Domon forces Napalmman to use a Dimensional Chip, thus sending him on a rampage, it's Nenji who brings the outraged navi back to his senses. Domon is never seen again after this incident, and Napalmman (whom Nenji renames as Nenjiro, much to the navi's dismay), is permanantly bestowed to Nenji.

Domon is just one big creep - it's good to see him hauled off to jail in the end.
This character description was made for episodes that I have seen so far. It may be updated as more episodes become available.