A large-breasted young woman from the village of Littner. Yoko has considerable combat experience even before her chance meeting with Kamina and Simon. When a Gunmen crashes through the roof of Giha village and prepares to attack the populace when Yoko, who has been tracking the Gunmen, rappels down a cliff whilst firing her electromagnetic rifle. Her solo attack disables the Gunmen, giving Kamina and the villagers time to seek safety. Kamina, however, chooses instead to make advances at Yoko and initially diminishes her combat qualifications on the grounds of being a woman, yet acknowledges "that lady's spunk".
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. Although Yoko is only slightly older than Simon, 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.
After the war of liberation, in which she plays a major role, Yoko eschews taking part in politics at Kamina City. Desiring to distance herself from her warrior past, she takes the name Yomako and moves to remote Koreha Island. There, she accepts the job of teacher at that island's elementary school. However, after learning of events occurring at Kamina City,and being attacked by 2 gunmen she temporarily leaves the island and breaks into Rinkane Jail to release Simon. After leaving the prison with Boota, Simon and Viral, she joins other members of Team Dai-Gurren and pilots the Dayakkaiser to prosecute the war against the Anti-Spirals.
In the epilogue an older Yoko is seen at the same school mentioned earlier, but in the role of principal.