Kusanagi

Kusanagi (月輪割り断つ天龍の大爪, lit. Moon-Severing Sky Dragon's Talon) is a Noble Art used by Ouma Kurogane.

Description
Like Katharterio Salamandra of Stella, Ouma channels his magic into his Ryuuzme compressing the wind around it, devouring the atmosphere, causing layers and layers to all be stacked together turning it into a powerful sword of storming wind, which expands up to over fifty meters in height. At first, it was able to overpower even Katharterio Salamandra in his initial battle with Stella and it turned the school buildings, practice areas, asphalt into rubble.

Weakness
Kusanagi's power depletes with each usage, although with the third usage, it was still strong enough to withstand Nene's Black Sword・Yatagarasu. It also requires some time to activate.

Trivia

 * Kusanagi is named after a one of the Three Imperial Regalia of Japan, also known as Ame-no-Murakumo-no-Tsurugi and later Kusanagi no Tsurugi, which is explained to be able to manipulate wind.