Yukina Kiritani

She is Yuuya's childhood friend who is a year older than him, she returned home after a long absence. She use to maintain a boyish look where she would often be mistaken for a guy, until her return when she sported a girlish look. It is hinted that she can sense Hiyori's presence and may even be aware of Mitsuki's predicament. Hiyori would often refer to her as "Top Heavy Woman" because of her bust size. (Source: Manga-reader)