Kasumi Saegusa

As the elder of the Saegusa twins and Mayumi’s younger sibling, this spirited tomboy serves as the complete personality foil to her twin sister, Izumi. While she originally viewed Tatsuya with deep suspicion, her initial distrust has since evolved into genuine respect for his abilities. Her bold, energetic nature stands in stark contrast to her sister's more reserved demeanor, marking her as a distinct and formidable presence within the Saegusa family lineage.