Karakurenai

«Karakurenai» is the curved katana used by the guild leader of «Fuurinkazan», Klein. This sword allows the usage of the uncommon «Katana» Extra Skill, which is unlocked by training the «Curved Sword» skill sufficiently, and its respective Sword Skills.

Klein most likely uses Karakurenai up to and including the clearing of the 75th floor of Aincrad.