Also known as: 七つ夜, 七ツ夜
Tohno Shiki's main weapon in Tsukihime, whose name translates to Seven Nights. An antique knife inscribed with the name of the Nanaya clan, and later given to Shiki.
It is a Switchblade with a plain hilt, with its blade and hilt of a length around 10cm. The blade can alternately be called the Nanaya.