We are not 'sexy', we are 'sexual' and 'sensual. And we might be with anybody we respect as a human being equal to ourselves. They just have too many socially-indiced hang-ups to feel emotionally free and without emotion what is sex worth?
If you want to know, INFP's are basically innocent, but are curious about others, so become other types to fit in. However, when secure, safe, and feel that we can be ourselves, we are romantics in the sense that we don't use romantic gestures, we are romantics embodied. We are romantics in that we will talk, think, and express romance in all we do. We have no basis in reality, and so can be free to believe in love as tangible and present. As for sexy, we are like princes and princesses in that sexiness is a given, just as everything else is for us. Think of an INFP as a prince or princess and you can't go wrong, since we don't take titles seriously, and are very humble about it. Our rich fantasy life makes others feel as if they are part of the fantasy, and if that's not sexy then what is. If you need something, we are there, and are curious to try anything the first time. Basically, we are sexy when we are confident enough to be ourselves, and who wouldn't want someone who's romantic all the time?
INFPs are forgiving and understanding; they will make the effort to keep a relationship solid. An INFP would probably make a good mate. 'Sexy' is probably not the best word because these are qualities that can go unseen, especially in a wallflower, and may not enter the picture when sexual attraction is considered.