In my opinion,there are no differents between a holy grail and a holy girl.They all have a simple truth to define it.For a holy gril,every one know she must not have make love with anyone.Perhaps someone would like to belive a holy grail must contains complex mathematics.On the contrary,a holy grail has the same simple truth compared with a holy girl.
For example,I ever heard of the define of the trend which everyone prefer to follow.The trend means a series of higher or lower points which in the same order.Then the breakout of letter "N" will be useful for you to grasp the trend.I further wrote following system to explain such a holy grail in order to again my view of the same simple truth.