Kagero is Japanese for thermals, the shimmer of hot air (it also translates to heat hazes, shimmering, and mirages). Kagero was the name of a leading destroyer-class ship in the Imperial Japanese Navy during WWII. A more explicit meaning is: "The Shimmering Mist that Rises from the Earth on a Hot Day." All but one Kagero was lost in the war. The only surviving Kagero was the Yukikaze.
Great Katana skill level 100 is obtainable by the following jobs at these corresponding levels: