Akari Kosugi is the younger sister of the protagonist, Takuma Kosugi. She is characterized by a cheerful and outgoing personality, which allows her to quickly form a close bond with her brother's wife, Mina. A defining aspect of Akari's character is her strong fascination with interspecies romance, a personal interest that fuels her curiosity and support for her brother's unusual marriage to a robot. Her role in the story is primarily that of an ally and friend to the couple. She actively embraces Mina as a full member of the family, treating her not as a mere household appliance but as a real woman and a sister-in-law. This is demonstrated through her actions, as she spends time with Mina by taking her shopping and enjoying casual conversations, becoming a confidante and a friend with whom Mina can have girl talk. Akari's key relationships are with her brother, Takuma, for whom she has a great deal of affection, and with Mina, whom she treats as a true companion. Her development within the narrative centers on her growing friendship with Mina and her supportive role in normalizing and celebrating the couple's unique relationship.