Totsuka-no-Tsurugi, literally meaning "Sword of Length of Ten Fists", is not a specific sword, but a common noun for any sword of this length. In Japanese mythology, numerous deities own a sword of this kind. There is one particular Tsurugi, that was used by the god Susanoo in order to slay Orochi the Eight Headed Serpent.
According to legend, after the sword's owner, Susanoo, was banished from Heaven by the reason of killing one of Amaterasu's Attendants and destroying her rice fields, he descended to the Province of Izumo where he met Ashinazuchi, an elderly man who told him that the Yamata no Orochi, who had consumed seven of his eight daughters, was coming soon to eat the last one: Kushinada-hime.
Susanoo decided to help the family and investigated the creature, soon he begged Ashinazuchi for permission to marry Kushinada-hime, which was granted; having his plan ready, he transformed his wife into a comb so he could have her near in the battle.
As the great snake came, it put each one of his eight heads through the gates the god built, searching for the daughter; as a bait the god had put big amounts of sake after each gate, the snake took the bait and got drunk; having an easy chance, Susanoo took the Worochi no Ara-masa and cut every head off the snake, proceeding with the tails, in the fourth one he found an exceptionally great sword, the Kusanagi-no-Tsurugi.
Having the sword in his hands he returned to the heavens offering the sword as a reconciliation gift to his sister Amaterasu.