Nagisa Kashiwagi is a classmate who occasionally asks Kaguya about what to do in her relationships. The daughter in a wealthy shipbuilding family, she academically ranks in the top ten of the class and heads the school's Volunteering club. Nagisa exhibits many girlfriend behaviors such as talking a lot, being moody, or even jealousy to the point where she hires a private detective to spy on her boyfriend to see if he is having an affair. She initially starts asking Kaguya for relationship advice.