Because of Youmu's spellcard "200 Yojana in One Slash," she is said to be capable of striking at speeds most would consider physically impossible (200 yojana can be a distance anywhere from 1,320-3,000 kilometers or 825-1,875 statute miles in length). In order to cover that kind of distance in the split-second a typical sword slash takes to execute, she would have to be capable of moving at far beyond hypersonic speed; her slowest sword slashes have been calculated to move at speeds in excess of Mach 70 (70 times the speed of sound, or 53,200 mph/85,120 km/h at sea level), fast enough to circle the entire Earth at the Equator in less than half an hour and around three times the speed required to orbit the Earth, for reference. One doujinshi (Touhou Kaidan Seven #3) went into far too much detail trying to work out the specifics of this, and determined that her theoretical top speed was approximately one quarter of the speed of light...
