You can try looking for it in local bookstores. Some big - name bookstores often have a wide selection of light novels, so there's a chance they might carry it.
Well, another place could be Tumblr. There are often fanfic recs (recommendations) on Tumblr. Some users might share links to their favorite 'Kiss Him Not Me Shinomiya' fanfictions. You can also search Tumblr using relevant tags. However, the content on Tumblr might be a bit more scattered compared to dedicated fanfiction sites, but it's still worth a try.
Since I'm not familiar with 'kiss him no me light novel', it could potentially be a story centered around a female protagonist who is conflicted about her feelings towards a male character, which is represented by the 'kiss him no me' concept. Maybe it delves into her internal struggle between her emotions and her self - restraint.
As mentioned before, 'lemon' content is inappropriate, so I can't really discuss the characteristics in that regard. But in general 'kiss him not me' fanfiction, it often focuses on the romantic relationships between the characters, exploring different scenarios and emotions within the context of the anime's story and characters.