Raikiri

Raikiri (雷切 Raikiri) is one of Kusakabe Seven Swords, sealed in the ring finger's nail of Misuzu Kusakabe. The sword is of thunder element and its shape also somewhat resembles a lightning bolt. Its lightning can be used to strengthen melee power or attacking many enemies from a distance. Due to its versatility, this sword is mainly used by Kakeru Satsuki.

Overview
The sword is said to have been the property of a samurai named Dousetsu Tachibana (立花道雪 Tachibana Dousetsu) long ago. The man attempted to cut a lightning bolt with the sword. What happened to him was unclear; some said that his whole body was burnt while some claimed he lost the functions of half his body. However, in exchange, the katana gained the power to emit lightning, hence the name "Lightning Cutter".