Seiko had a reserved personality and a stilted way of speaking. As a pharmacist, she had an extensive knowledge of medicine and drugs. She created many different kinds of drugs, including ones that can drastically change one's physical appearance and make them much faster and stronger.

Seiko is shown to be somewhat pessimistic. In a flashback showing how she met Ruruka, she spends her time lamenting the death of 1 dog rather than cherishing the life of the dog she saved. She also appears to sho