Kammala jumla mai zuwa: Yamaguchi ya yi gasa a matsayin ɗan shekara goma sha takwas kuma memba na ƙungiyar Japan a cikin wasannin relay biyu na 'yanci a Wasannin Olympics na bazara na 2008 a Beijing. Duk da rasa wurin mutum a cikin mita 200 na 'yanci, ta yi nasarar zama ta huɗu a gwajin wasannin Olympic a Tokyo (2:01.64) don samun cikakken zaɓi a cikin tawagar relay. Yin aiki tare da Haruka Ueda, Maki Mita, da Emi Takanabe a cikin
4 × 200 m freestyle relay karshe, Yamaguchi ya yi iyo a mataki na biyu tare da raba 1: 58.51, amma dole ne ƙungiyar Japan ta zauna a matsayi na bakwai a cikin 7: 57.56. Yamaguchi ya kuma halarci tseren tseren tseren tseren mita 4 × 100 tare da Ueda, Mita, da Asami Kitagawa, amma ya rasa daga cikin manyan 8 na karshe ta hanyar 0.08 na biyu a cikin lokaci na farko na 3:39.25.