Yoriko Yasaka (八坂 頼子 Yasaka Yoriko?) is Mahiro's mother, a monster hunter who started her career during college. She has a young appearance that makes it hard to believe that she has a son in high school. She conceals her true job from her son until returning home during the plot. She is kind to friendly aliens, accepting Nyaruko, Kūko, and Hasuta living in the house, and their actions to pursue Mahiro. She advises Nyaruko to take her relationship with Mahiro a bit slower at first, but permits their relationship later after they rescued her. She also has a habit of hugging Mahiro.