Red Obsidian (草薙の剣) is a Katana. It was retrieved by Kodoh and has since then become his main weapon. He claims the weapon is extremely difficult to wield, and if it weren't for his training, he wouldn't be able to handle the Sword.
Red Obsidian is stained with the blood of its victims. It is impossible to wipe away the blood, as it has soaked into the Obsidian and dried, making it apart of the blade. It is filled with traditional Japanese markings on it. Iron and Obsidian were both used in making the Sword, hence the name.
Kodoh's knowledge about weapons lets him use Red Obsidian to its full potential. He can easily shatter weaker blades, deflect attacks from large blades, and even fend off against multiple opponents at once. The katana is extremely light, flexible, and durable. This makes it the perfect weapon for Kodoh to wield.
- It was named after a material in Minecraft.