Rihoko, younger sister of former Ninku corps captain Toji, enters the story after Fuusuke rescues her from kidnappers posing as Ninku operatives. Unaware of Fuusuke’s history with her brother, she accompanies him to locate Toji, eventually reuniting with her sibling and joining the core group alongside Fuusuke, Toji, and the aloof Aicho.

As the team clashes with the Imperial Army—determined to eradicate remaining Ninku members and turn public sentiment against them—Rihoko’s involvement deepens. Her dynamic with Aicho introduces friction, marked by her persistent romantic overtures and his dismissive rejection rooted in a broader aversion to women.

Integrated into the group’s mission to dismantle the Imperial Army’s schemes and expose the truth behind the Ninku’s defamation, Rihoko reinforces themes of loyalty and family, exemplified through her unwavering bond with Toji. Her presence bridges personal stakes and collective resolve, anchoring the narrative in both strategic conflict and intimate relational tensions.