Yonaka is depicted as a doting younger sister who loves her brother. She admires her brother greatly, wishing for nothing more than to see and be together with him again, due to him leaving her and their family sometime when she was in Junior High. She is a very serious, kind, and accepting girl; she was quick to accept cooperating with Defect Mogeko, despite not being wholly aware of the reasons concerning his imprisonment. Her hobby is eating candy under the stars.