I know the fact that Kirito's Dual Wield in SAO was an award or was awarded by the system for being the top player with the fastest reaction time. see here
And that Yuuki can pass down her insane sword combo - 11 hit (Mother's Rosario) to other players like Asuna. (Because kirito is having a hard time reproducing Starburst Stream in ALO which is 16 hit combo, as stated here)
But how did Konno Yuuki create this skill? Or is it just a skill which came from her converted account because she was in some other VRMMO?
Is there a chapter in the light novel / manga where this is discussed?