Galilei Donna: Kazuki Ferrari

 Kazuki is the middle child of the Ferrari sister and a descendant of Galileo.  Despite being a bit timid and prone to worrying she is a skilled black belt at a form of Kung Fu called 'Shorinji Kempo'.  She is also a good cook.  Unlike her sisters she would prefer to stay at home and will often times skip class to avoid group activities.  

Yamada's First Time: Kazuki Kosuda

Kazuki is the tomboyish college age older sister of  Takashi Kosuda.  She often helps her younger brother in his attempts to get closer to Yamada.