The Sora Katana is the main weapon that The Hero wields.
The Sora Katana is a Kusagari heirloom. It is unknown how it is made to everyone except for the Kusagari clan. The weapon itself is made of unconventional materials that give it overwhelming power. It is so powerful, many other clans seek to claim it.
In Red Steel 2Edit
In Red Steel 2, the katana was the reason for most of the events in the game. It was stolen by Payne, the leader of the Jackals. When the Hero defeats Payne in a duel, he gets the Sora Katana back. It is later revealed that Shinjiro is behind the massacre for the sword, going so far as to hiring other factions for it. At the end of Red Steel 2, The Hero defeats Okaji, and finally Shinjiro by fatally stabbing him on a rock, then breaking the katana in two to end the struggle of power for it. The Hero ultimately throws the handle over the cliff, leaving it's true fate unknown.