A Course 2 student and Tatsuya's 1-E classmate. She is one of the first people to befriend Tatsuya, and is close friends with Mikihiko, Leo and Mizuki. Very much a standard tsundere, she has an outgoing personality that allows her to befriend people easily but she garners attention from those around her and is someone who is not easily committed and goes off on a whim. While she and Leo got off to a rocky start, it's clear that eventually there may be more than just friendship between the two.

A beauty in her own right, Erika is the youngest daughter of the Chiba Family, one of the Hundred Families, famous for training people in swordsmanship. She greatly admires her older half-brother Naotsugu (almost to the point of having a brother complex) and disapproves his relationship with Mari Watanabe. She herself is a master of swordsmanship, enough for her to be recognized and allowed to carry the Chiba family name. During the Yokohama Disturbance, she wielded the giant sword Orochimaru, one of the pinnacles of sword-type armament forged by the Chiba Family.