Kitahara Nayuta

Nicknamed Nayu. She is a first-year student of the Arts Department at Chihaya University, the same university Shougo attends. Nayu is full of energy, her presence always brightens up her surroundings. She loves designing avant-garde sculptures.

Spoiler

She and Isako are step sisters by way of Isako's dad marrying Nayuta's mom after the death of his wife.

Nayuta suspects that she may actually be the illegitimate child of Isako's dad and thus Isako's half-sister.