This one was her debut song that made back in 2006. Although it was her 1st song, but the Fate/stay night OP song was a hit during that time. The melody was pretty calm & rhythmic. If you want to rest up your mind, you can listen this kind of song.
If you love Fate series, you should watch Fate/stay night first. But the ongoing prequel of the anime Fate/zero is getting better. Graphics & animation are top notch and the plot is getting intense now.