* 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 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...
* During some of Youmu's spellcards time appears to slow down while she performs her sword slashes. This is not due to any innate time-stopping power such as the one Sakuya has; rather, it is simply Youmu moving so fast that relative time slows down for her (Einstein's special relativity theories hold that at extremely high velocities time moves slower for those traveling at that velocity than for a stationary observer). For the record, moving at this velocity should vaporize her and her sword from the air friction heat... thank goodness for magic.
( ﾟ 3ﾟ)~♪