Midori's sword, a traditional Japanese katana.  It is a family heirloom of 1500 years of age.  An excellent tool for demon-slaying, it is also a holy relic, capable of damaging even the mightiest of supernatural foes such as Kyoro.  In addition to its sharp edge, there is another interesting feature; according to Midori, as long as the wielder's will is unbroken, the blade shall not break.  The sheath is also extremely durable and special, as evidenced during her battle with Lucia.