Rika Kawada, a character featured in official franchise media, is the 20-year-old younger sister of Yura Onoda, distinguished by her blue hair and eyes. A college student, she belongs to a family comprising parents Hideki and Chiharu Kawada and gains additional in-laws through Yura’s marriage to Makoto Onoda. Openly promiscuous and sexually experienced, she balances a primary boyfriend with three casual "sex friends," accumulating 30 partners. Her dynamic includes teasing Makoto and Yura about their sexual inexperience, prodding them to enhance their intimacy.

Initially entangled in an unstable relationship with boyfriend Taku Yamada, she later pursues stability by marrying Katori, son of Makoto’s employer, though the union collapses swiftly due to personal incompatibilities. Her narrative traces a shift from transient encounters to a fleeting marital attempt before reverting to juggling four boyfriends. Despite her own chaotic romantic history, she vocalizes concern for Yura’s marital satisfaction, dispensing unsolicited advice on sexual matters. Her interactions with the couple underscore her role as a provocative contrast to their naivety, positioning her as both agitator and self-styled mentor in their relationship.