Kaoruko Seibu, daughter of Seibu Railway Company president Tetsuzo Seibu, possesses intelligence, beauty, and a strong will, presenting a regal demeanor that masks a secretly dreamy, romantic nature. Once resolved, she acts decisively and is quick to fall in love. During university, she contributed to the amateur literary publication *Azalea*. Born October 18th, a Libra with blood type B, her hobbies include travel and she plays the piano skillfully.

Her background holds an unresolved childhood memory: treasured recollections of an unnamed boy met in Chichibu. She remembers walking with him through Chichibu Shrine, viewing pink flowers at Hitsujiyama Park, experiencing the mountain stream at Nagatoro, and observing the sea of clouds from Mitsumine Shrine. These moments remain deeply significant, though she never learned his name. As an adult, facing an arranged marriage meeting with Akifumi Nasa—son of a powerful industrialist, arranged by her ambitious father to further his new space venture—Kaoruko remains unable to forget this encounter. Clinging to faint hope, she resolves to revisit Chichibu alone to search for the boy, yearning to relive those memories and possibly reunite, prioritizing this quest over her father's expectations.

Her journey reflects her independent spirit and emotional commitment to resolving her past. Physically, she has dark brown hair and aubergine-colored eyes. Her story involves revisiting the specific Chichibu locations tied to her memories—Chichibu Shrine, Hitsujiyama Park, Nagatoro's Iwadatami rocks, and Mitsumine Shrine—driven by determination to find closure.