Natsumi Suga, a university student and niece of Keisuke Suga, works part-time at his small publishing firm, K&A Planning Co., Ltd., researching urban legends and supernatural phenomena. Estranged from her father, Keisuke's older brother who held a government finance position, she left home to live with her uncle in Tokyo; her mother remains unmentioned. Natsumi exhibits a carefree and mischievous personality, playfully teasing others like when she embarrassed Hodaka Morishima for staring, yet demonstrates deep kindness, loyalty, and protectiveness. She cares for her uncle, bonds genuinely with Hodaka and Hina Amano, and warns Hina about the dangers of being a "Sunshine Girl." Her enthusiasm for the supernatural contrasts with her uncle and Hodaka's more financially driven interest. Physically, she has long brown hair often in a ponytail and distinctive purple eyes. She favors casual clothing exposing her arms and legs, accessorized with nail polish and wristbands. Natsumi significantly drives the plot: she connects Hodaka and Hina's weather business with clients, later aiding Hodaka's search for the vanished Hina after his escape from police custody. She transports him through flooded Tokyo on her Honda Super Cub motorcycle until the water depth forces a stop, leading to her apprehension. Three years later, she maintains close ties with Keisuke, Nagi Amano, and Moka Suga, seen in Keisuke's photos. While not undergoing a dramatic internal arc, she consistently displays resourcefulness and bravery, willingly engaging in legally dubious activities like aiding Hodaka's fugitive status to support friends. Personality assessments categorize her as an ENFJ and Enneagram Type 5w6, reflecting traits like curiosity, protectiveness, occasional emotional detachment, and prioritizing personal loyalty over societal rules.