Miyuki Mochizuki comes from the same clan as Shinji. The two are good friends, and maybe something more. As children, she was the closest one to Shinji after he was reluctantly adopted into the clan.

She has been well trained in the arts of Kukishin-Ryu Ninjutsu by her father, the head of their clan. Aside from being a master of weapons, she is also skilled in hand-to-hand combat. In addition, she is an expert in kunoichi techniques, such as making herself look innocent and vulnerable. A common phenomenon that occurs when she appears and disappears is that
she is seen surrounded by cherry blossoms.

Miyuki was the one who gave Shinji his sword, Hayabusa, which was modeled after Sasaki Kojiro's no-dachi. What she didn't tell him however, is that due to his deeming as a "runaway ninja", her father has ordered her to assassinate the swallow in order to keep the secrets of their village from falling into the hands of their enemies. She loves Shinji too much to kill him, but only time will tell whether or not she will put her heart before duties.