Invite Home: Virgin characters in particular don’t want their first time to be sneaking into a private room or some seedy hotel.Even at Low/Lowest virtue, a character is more wiling to have sex if you’re in a relationship, even when love has declined. Become Lovers: This is necessary with Normal/High/Highest virtue characters.The lowest virtue may respond well to a grope without a kiss if Like or Love are high enough. Physical contact: Only the lowest virtue characters would agree to sex without at least a kiss, and may not accept a kiss without a hug, or a hug without a caress.Talk Lewd, Kiss, or Touch can do this, as can witnessing other characters engaged in sex.
This lists the requirements for getting sex in ascending order according to virtue.