Wikipedia
Futsunushi
In Japanese mythology, is a kami of swords, thus his Shinto priests are supposed to always wear Nihontō with them, at least in the shrine. He is a general for Amaterasu along with Takemikazuchi. He is worshipped at Katori Shrine, and as he is seen as a god of martial arts, Katori Shintō-ryū adepts make a solemn oath when they join the school.