Nanase Tsukumo is the homeroom teacher for Yuuta Togashi, Rikka Takanashi, Shinka Nibutani, and Makoto Isshiki. She has short brown hair and blue eyes. Her personality is passively caring, showing deep concern for her students' welfare. She enforces rules fairly, disciplining those who make mistakes or break them.

She supported student initiative by approving the formation of Rikka's club, the Far-East Magical Napping Society – Summer Thereof, after its members responsibly cleaned an excessively messy designated room.

Tsukumo appears consistently throughout both seasons of the main anime series and maintains her role in the movie "Rikka Version," documented across these core animated adaptations. Her interactions reflect her position as an educator focused on maintaining order while facilitating appropriate student-led initiatives, functioning as a stabilizing and supervisory figure within the school setting for the main student characters.