The Sword of Dark Space (暗い空間の剣 lit. Kurai kūkan no ken Viz. Dark Blade) is a weapon used by Houou, and was previously owned by an unknown ninja that he killed in battle. The Sword of Dark Space is a curved longsword with a black edge produced by what Houou calls "Physical Shadows". The blade is capable of repairing itself when broken by simply being immersed in shadows.