Yagyu Shinkage Ryu is a famous sword school. Unfortunately this Ryu has lost its shurikenjutsu but the densho still show drawings of shuriken in them including this one.
Thanks to Mark Lithgow a member of Yagyu Shinkage Ryu for providing information on this shuriken
Thanks to Mark Lithgow a member of Yagyu Shinkage Ryu for providing information on this shuriken