Doujigiri Yasutsuna

Doujigiri Yasutsuna (童子切安綱 Doujigiri Yasutsuna) is one of the Kusakabe Seven Swords and is also the most powerful. It is sealed in the thumb nail of Misuzu Kusakabe.

This powerful sword devours life energy of the wielder and turn that energy into great power. When used, a pair of demonic-looking arms will grow from the handle and squeeze the wielder's arm, hurting Misuzu when she uses it in the process. The more energy the wielder allows it to consume, the higher the arms will reach.

Its full power isn't shown in the anime, but it's shown being powerful enough for warding off Lieselotte's attack and shooting a strong fire spell to counter that Lieselotte would avoid.

In the manga, its powers largely mirror that of the visual novel. Misuzu was also capable of using Kumokiri's curses with Doujigiri, enabling her to finally defeat Misao Kusakabe.