Sena Narumi attends Sakuragaoka High School, possessing long blonde hair inherited from her mother Ayako and blue eyes from her father Yusuke, standing 160 cm tall. She often layers her school cardigan under her blazer. Outside school, her wardrobe showcases feminine and trendy pieces reflecting her modeling career; as a child, she favored pigtails decorated with star accessories.

Scouted in middle school, she works as a teen fashion model. Beyond modeling, she designs fashion, founding the makeup brand HANICOS and the fashion brand Honey×Honey. She maintains good academic performance alongside her busy career.

Positive, friendly, and valuing authenticity, Sena inspires peers like Arisa Takamizawa and her younger sister Mona. Romantically, she is initially shy but becomes assertive, often initiating contact during dates. Her relationship with classmate Midori Hamanaka starts after silent Friday subway commutes; lending him her umbrella during rain sparks their connection. She affectionately calls him her "prince," and they secretly date, with Sena as the more active participant.

As Mona's older sister, she actively supports Mona's idol career, attending live performances when possible, promoting concerts, and monitoring Mona's progress by watching all performances live or later. Her celebrity status leads to admiration from Arisa Takamizawa, who inquires about her modeling work during high school interactions.

Professionally, she collaborates with the male idol duo LIP×LIP for music videos and brand promotions like the "Romeo" video and "Koi wo Shiyou" series for HANICOS, maintaining a strictly work-based relationship.

She was in Class 1-1 during her first year at Sakuragaoka High alongside Akari Hayasaka, with whom she has been friends since middle school.