Eri Amakazari, who is almost always called by her nickname Ecchan, is a middle school student attending CITY South Junior High School where she is in her second year. She is best known for being the closest friend and constant companion of her classmate, Matsuri Makabe. The two girls are so inseparable that they form a duo, spending most of their after-school time together in what they playfully call their "Going Home Club". Rather than heading straight home, they embark on their own little adventures around the city, often spontaneously inventing imaginary clubs and scenarios to act out for their own amusement.

Ecchan is a kind, supportive, and highly imaginative girl whose energy and creativity are central to her friendship with Matsuri. She is often the one who initiates their games and comes up with the topics for their adventures, taking on a more dominant role in their dynamic, while Matsuri plays along eagerly, often bestowing elaborate and humorous titles upon her, such as "Demon Lord Emperor". Despite her playful and eccentric nature, Ecchan can also display a surprising degree of maturity and consideration for others. Her warmth is demonstrated in her interactions with adults in the community, such as when she visits an elderly barber named Kuratake. To save her parents money on haircuts and to keep the lonely old man company, she becomes a regular customer, even offering to be like a granddaughter to him, which earns her his deep respect.

The core of Ecchan's motivations and role in the story is her precious friendship with Matsuri. Their relationship is the heart of their shared adventures, and Ecchan deeply values the time they spend together. This is thrown into sharp relief by a significant plot development: Ecchan's family is preparing to move to England after the summer. This impending departure adds a layer of melancholy to her final weeks in the city, making their time together all the more meaningful and providing a poignant emotional core to her storyline. Another key relationship involves a boy named Takewaku, for whom Ecchan briefly harbors a one-sided affection. However, after discovering he is dating someone else and discussing her feelings with Matsuri, she concludes that her feelings were not truly romantic and that pursuing a relationship would only take time away from her best friend.

Ecchan is physically characterized by her short blue hair and blue-grey eyes, and she is almost always seen in her school uniform. Her development over the course of the narrative revolves around navigating her strong, platonic love for her best friend and facing the reality of their imminent separation. Her notable ability lies in her boundless creativity and imaginative spirit, which allows her to transform ordinary after-school hours into a series of fantastical and memorable escapades, turning the mundane city around her into a playground for her and Matsuri.