Young and annoying, she dreams of becoming the greatest Tekkaman in the world. She looks up to D-Boy (Slade) and falls in love with him (she calls him the "White Tekkaman" and thinks he is a knight in shining armor). He saved her life when she was younger. Yumi is rash and immature, crying about everything, but she is indeed a powerful Tekkaman, Tekkaman Iberu. Once she learns to use her powers, she becomes very effective and actually manages to help Blade improve his skills when he fights Dead.