Westonji Ruiou, a member of the Special Crimes Unit. Five years ago, she lost her older sister, Mayo. Mayo was also part of the Special Crimes Unit and an excellent detective. However, while undercover investigating the notorious criminal organization Mantis, she tragically died during the course of her investigation due to an accident that remains shrouded in mystery. Driven by vengeance and fueled by her unwavering determination, Ruiou continues to pursue Mantis, relentlessly seeking justice for her beloved sister.