Age: 14
Birthday: September 29, 1987
Blood type: B
Height: 152cm
Weight: 39kg

Shinobu, who is Mikoto's real sister, is a ninja, but became infatuated with samurai and set out on a journey to train herself. Because of her horrible sense of direction and clumsiness, she gets lost deep in the forest and does not find out about Ikuto's arrival until much later. Hearing that Ikuto's a great sword master who defeated the Leader of the North in a swordfight, she stubbornly persists in her request to spar with Ikuto for days until he agrees to do so. After Ikuto 'defeates' her, she becomes Ikuto's disciple in swordsmanship, owing again to her extreme stubbornness that Ikuto doesn't wish to put up with after already experiencing it.

Because Shinobu is so obsessed with becoming strong and sparring, she doesn't know 'love'. This has been illustrated quite a few times. During her match with Ikuto, when he accidentally grabbed her breasts, she didn't know what kind of feeling she had at that moment. At another time, when every other girl was hoping that Ikuto would pay them a visit in their room because that would be a sign he loved that girl the most, Shinobu thought Ikuto would come to her room to spar. She does however start to become jealous of others receiving attention from Ikuto such as Rin and Suzu, once seeing Suzu be patted on the head by Ikuto, she becomes fixated on Ikuto praising herself in the same manner.

Like most inhabitants, Shinobu also has an animal who follows her day and night, a cow named 'Beef Jerky'.