Taromaru is one of the two giant spider, servants of the Spider Goddess Naqua.
In manga Kaibutsu Oujo its name was called the first time by Naqua in chapter 50, volume 11. Its 1st appearance may be in chapter 30 volume 7, as a giant spider.
In manga Naqua-den, its body perish some 10 years ago in a battle between Japanese gods and goddesses defeated the invasion of Russian goddess of ice. Its spirit reside inside the boy Tarou Kanda to rest and recover. Presumably the boy's voracious appetite come from the spider's need to have more energy. Naqua insist on calling Tarou Kanda "Taromaru" just as Tarou insist on his name.