A second-year student, Sumida is one of the members of Ms. Mogawa's Hole-Digging Club, who was once known as the club's "ghost member" due to her being absent for most of the time. She is the senior of Shijima Tsukishima and Majime Yamashita at her own school. She's A rather silent person, Sumida does not usually talk through verbal communication, but instead she uses a notebook as means of communicating to others by writing her dialogues on it. Sumida is also known to be a competent drawer, whom she also draws art in her notebook, when she sometimes communicate. She is an avid fan of Ms. Mogawa's doughnut-shaped sculptures.
