Riko Izumi is a student in class 2-3 at CITY South High School and Wako Izumi's younger sister. She is often seen to be sleep-deprived and would often fall asleep whenever given the chance. Unbeknownst to her, she is able to capture the hearts of everyone who interacts with her in the city, even garnering a fan club composed of various city residents in an attempt to smooth out any potential conflict from anyone striving after their mutual crush. Despite her obliviousness of her surroundings thanks to her usual lack of sleep, she seems to have an affinity with robotics, as she have constructed several robots in her youth and have even shown to be a capable hacker, a skill that her sister relied upon to disable the machine utilized by the Makabe-Adatara pair.