Seichiro Toba serves as head of education at Kyowa College, an institution established by Sukaza Ryudo, grandfather of the four Ryudo brothers. He simultaneously holds the position of headmaster at Kyowa Institute. Driven by financial ambition and the goal of becoming Tokyo's head of education, he employs unethical tactics, including deceiving his own family members. His actions directly cause Hajime Ryudo to lose his directorship at Kyowa College.

He is married to Saeko Toba, Sukaza Ryudo's daughter. This marriage makes Saeko the aunt of the Ryudo brothers and Seichiro their uncle by marriage. The narrative implies Seichiro may have married Saeko strategically to secure his headmaster role. The Ryudo brothers hold significant respect and affection for Saeko, contrasting sharply with their profound dislike of Seichiro.

Seichiro is the father of Matsuri Toba, cousin to the Ryudo brothers. Matsuri expresses extreme contempt and embarrassment toward her father due to his self-serving and greedy conduct. The Ryudo brothers share this negative view, deeply distrusting Seichiro specifically for his willingness to exploit family ties for personal advancement. His role consistently generates conflict within the family through manipulative schemes aimed at gaining power and status.