Having lost Asamiya Saki, Sukeban Deka I, Kurayami has been looking for a successor, but he has been having trouble finding the perfect candidate. One day, his subordinate Nishiwaki brings him information about Godai Yoko, who has been brought up in Tosa wearing an iron helmet (Tekkamen).
Yoko is taken to Tokyo and Tekkamen is removed by Nishiwaki but she refuses to join up with Kurayami's organization. He confines her in the basement of his mansion. Nishiwaki tells her that her eyes resemble her father's a lot. He seems to know about her father. He also tells her that she could open an opportunity in her life by being a Sukeban Deka.
Kurayami offers her a condition to free her from confinement. She must defeat 10 armed men. He observes how strong she is and he is more impressed.
She is freed, and she agrees to be the Sukeban Deka with the name Asamiya Saki and accepts a cherry-blossom-embossed yo-yo to learn the secret of her birth and her father's death.
