Athena Imai is the younger sister of Maria Imai, a member of the East Oizumi Academy Cosplay Club. At 11 years old with purple hair and red eyes, she is too young to attend the academy but regularly joins the club's activities. She struggles with shyness during costume presentations, often needing Maria's help to dress.

Maria is fiercely protective of Athena, especially against unwanted attention from other club members. Jenny Matel, an Italian exchange student in the club, develops an inappropriate attraction to Athena due to her youthful innocence, leading her to repeatedly attempt physical contact. These advances cause Athena significant distress and anxiety. Maria frequently faints upon seeing Jenny interact with Athena.

Athena accompanies the club to various events and training exercises, including a summer camp trip to a hot springs facility. Her presence fuels ongoing character dynamics and comical situations centered on Jenny's persistent pursuit and Maria's protective interventions. The existing media depicts no significant character development or background expansion beyond these core relationships and reactions.