Erio is Makoto's first cousin. One day in June the previous school year, while she was a first-year in high school, she mysteriously disappeared for six months, with no memory of what happened during that time. At the same time, she began having an extreme fascination with aliens, believing herself to be an alien investigator monitoring humans, up until Makoto helped her face reality.Erio is almost always barefoot, even when outside. Initially she is soft spoken and unsociable. Eventually, she opens up by gaining a part time job at her great-grandmother's convenience store and joins a baseball team. Her birthday has apparently been forgotten, but her family decides to celebrate it on June 7, the day after her mother's birthday.