Cthugha Atsushi, more commonly referred to as Kūko (クー子), is a prominent character in the anime series Haiyore! Nyaruko-san. She is a parody of the Cthugha entity from the Cthulhu Mythos, depicted as a passionate and fiery alien girl. Kūko is deeply infatuated with Nyaruko and often competes for her affection, leading to comedic and sometimes chaotic situations. Her role provides both humor and rivalry, adding a unique dynamic to the main cast.