A theory goes before the first shrine visit, Asuna's sex stats are only the ones Kirito knows about or with Kirito and after it is all of Asuna's experiences. If that is true then this gives a interesting picture of their sexual progress. Kirito has never had anal, footjob, blowjob, titsjob, or fondled her breasts. While the rest are understandable, Kirito has never played with Asuna's breast is surprising. So their sexual progression is probably: hold hands, kiss, vaginal sex, with some handjobs in-between.