She decides to accompany Simon and Kamina on their quest. Despite their constant banter Yoko soon becomes infatuated with Kamina. She is also the object of Simon's naive crush until he discovers the two kissing. Yoko is stated to be the same age as Simon, but it is heavily implied that her home-town measures time differently, as all humans live underground and might have a differing number of days in a year. She is very mature for her age and is the most rational member of the group. Those traits helped her to cope with Kamina's death although she remained affected by it.