Yumiko is Maya's elder sister and a doctor/CDC operator. She acts as a mentor to the fafner pilots, so they would have pleasant memories besides fighting.

She used to dream about being an idol in Tokyo before realizing the actual situation. Yumiko dated Michio before his departure, only for their relationship to rekindle after he came back.

She later moves in with Michio in order to make the best of what's left of their lives, and is the first naturally fertilized woman in Japan in 30 years.