Hizuki Yuiko

Ayumi, Mitsuna and Shino's older sister, as well as wife of Masakazu who is her distant relative. She met with Masakazu by chance and the two normally fell in love, then married.
Currently she is acting as a housewife and is living in Naoto's hometown. Because of various circumstances she has agreed to provide her body and give birth to Naoto's child, but they didn't manage to make one.
While feeling guilty towards her husband, her romantic feelings are slowly moving onto Naoto.
She feels motherly instincts towards Naoto.