Seiko had a reserved personality and a stilted way of speaking. As a pharmacist, she had an extensive knowledge of medicine and drugs. She’s pessimistic, hides her face behind a mask to make it less easier for people to guess what she was thinking through her facial expression. She’s easily startled and quite anxious, and shown to be quite shy as well during high school. She’s soft-hearted, taking requests from other students. and loves animals, providing care for an injured animal at no charge.