Zettai RyouikiAbsolute Territory
Zettai Ryouiki (絶対領域) roughly translates to "absolute territory" and is the area of bare skin exposed between a mini-skirt and thigh-high socks.
The ideal ratio is 4:1:2.5 (length of mini-skirt : absolute territory : length of over-knee socks above the knee).
There exists five "grades", from E to A. Only the top two (A and B) are considered true Zettai Ryouiki. The highest grade, Grade S, is a combination of Grade A, the ultimate level Twintails hairstyle and the ultimate level Tsundere attitude.
<--- Tohsaka Rin and her infamous Zettai Ryouiki.
Modified slightly for her Fate/EXTRA appearance.