Kumin Tsuyuri, a second-year student at Icho Private High School and senior to the main group, possesses an innocent, naive, and conservative personality shaped by a sheltered upbringing; she was homeschooled until high school due to her family's overseas moves for her father's work, resulting in old-fashioned ladylike manners. She exhibits a consistently carefree and gentle demeanor, creating a calm atmosphere, with her defining trait being an intense passion for napping as her primary hobby. Kumin carries specialized pillows for different seasons and weather, like her "sunny spring day pillow," and has been seen sleeping in a full futon on school grounds. Though her initial attempt to form a "Nap Club" failed from lack of interest, it found a home within Rikka Takanashi's "Far Eastern Magic Napping Society of Summer," where Kumin naps regularly as a core activity. Physically, Kumin has short dark brown hair, dark pink or aubergine-colored eyes, fair skin, a small mole on her right breast, and stands 154-155 cm tall. Despite her reserved background, she shows curiosity about unconventional things, frequently touching Makoto Isshiki's shaved head and enjoying violent or horror scenes. She earnestly supports her friends' chuunibyou delusions, striving to understand Rikka and Sanae Dekomori's fantasies even when confused. Her interactions often include sleep-talking and unintentional humor, such as later poorly received pun attempts. Her development includes temporarily taking on the "Tyrant's Eye" mantle for Rikka during the first season's conclusion. In the second season, she expresses a desire to emulate Shinka Nibutani's humor, though her jokes rarely succeed. During the movie "Take On Me," she proposes Yuuta and Rikka elope to prevent Rikka's sister taking her to Italy. Later, she travels to Aomori with Shichimiya to help resolve Rikka's internal conflict, while emphasizing the core issue rests solely between Yuuta and Rikka. Trivia notes include her surname "Tsuyuri" (五月七日) having an unusual kanji reading, initially misread by Yuuta as "Gogatsu Nanoka." She is fond of cats, evidenced by searching for a lost cat named Dodomen and her tendency to nap curled like a feline.