Which SAO girl is easiest?
All Kirito had to do was leisurely escort her through a world field he was vastly overleveled for and look heroic by crushing a group of PKers he outright admitted to her was no threat whatsoever to him. Comparing her to her sister (how?) sealed the deal, and lo and behold, she was moist for him.
The others had threats around them that required Kirito to actually break a sweat.
pic related, the others are already lusting for the Kirito D.