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Sonic Blade (高周波ブレード) is a close-combat Oscillation Type magic and is classified as a B-Rank lethal spell.
This spell can be applied to anything, giving the item the ability to cut easily. The item vibrates at extremely high frequencies, making it similar to a saw. The extremely high frequencies give rise to ultrasonic waves so practitioners of this technique often wear earplugs to block out ultrasound. 
It is a magic with limited applications, and apart from having an untouchable blade, it is similar to wielding a real sword.