Kaori Saejima is a resident of "Sky Castle," a luxurious residential complex where elite families live in a hyper-competitive environment. She is often seen as a role model by other mothers—specifically the protagonist, Sae Asami—because her son, Tetsuto Saejima, successfully gained admission to the prestigious Teito University School of Medicine.
Growing up in a musical family, Kaori was exposed to a wide range of genres and instruments from a young age. She began playing the piano and singing in her elementary school days and continued to develop her skills throughout her teenage years. After high school, Kaori decided to pursue a career in music, studying at the prestigious Tokyo University of the Arts.
