Mamimi Yamagami

An anime-exclusive favorite from the Sister Princess series, this classmate of Wataru arrives on Promised Island with a secret mission to separate him from his siblings. While initially tasked with spying, she eventually integrates into the family by posing as a thirteenth sister. As she witnesses Wataru’s deep devotion to his sisters, her perspective shifts, leading her to become a wise advisor. Though her role is limited in later adaptations, her impactful personality remains unforgettable to fans.