Renko Kamishakujii is a candidate for Student Council Secretary at Rikkyoin Academy. In the original OVA, she serves as a rival to protagonist Chihiro Enomoto's team within the student council selection tournament, representing an opposing faction.

Her character receives significant expansion in the 2006 television series. Renko exhibits a forceful and brazen personality, frequently wearing a white lab coat that embodies her self-styled identity as a mad scientist. This persona drives her to create numerous experimental inventions, including functional mecha units deployed on missions for the current student council. Despite expressing annoyance at collaboration and occasional frustration with team members' dispositions, she proves indispensable during various challenges.

Renko maintains a distinctive dynamic with Kaoruko Yamada, treating her as an assistant or subordinate. She routinely delegates tasks to Kaoruko and subjects her to verbal outbursts when her cheerful demeanor clashes with Renko's serious temperament. Their relationship develops when Renko perceives ingratitude from Kaoruko regarding new robotic assistants, leading to emotional distress and a reconciliation hinting at underlying attachment. Renko also exhibits a notable fondness for pandas, occasionally influencing her actions.

During a summer vacation episode, Renko's frustration with team interactions prompts her solitary departure to a family summer house. This isolation ends when circumstances involving physical danger facilitate a reconciliation, demonstrating her growing, albeit reluctant, acknowledgment of friendship's importance. Visually, she possesses purple hair, violet eyes, and glasses, typically accessorizing her school uniform with a neckerchief and knee-high socks.