Atoko identifies herself by that name but belongs to the Atlach-Nacha race of Great Old Ones, placing her among the cosmic entities of the Cthulhu Mythos.

She embodies a mischievous and provocative personality, acting as a "naughty prankster." Her degenerate conduct causes significant discomfort even to characters known for eccentricity, including asking Kuuko sexually explicit questions during casual walks and consistently pushing social boundaries. Her interests center on adult-oriented activities, as evidenced by Mahiro examining her browsing history to locate a dog image.

Dispatched to Earth to assist Nyaruko with a mission to protect the planet from annihilation, Atoko's specific task involved acquiring limited edition figures at a space comic market to create a planetary defense barrier. However, her role remained limited to delivering the initial assignment; she did not participate in the mission's execution alongside the main group.

Her presence primarily introduces comedic conflict through relentless teasing and boundary-testing behavior toward other characters, rather than driving major plot developments.