The ending of 'Kiss Him Not Me' manga ties up most of the storylines neatly. The main character finds love and resolution in a way that's satisfying for fans.
Well, there might be. You can try searching on fanfiction - specific websites. Some smaller, niche fanfic communities also might have 'kiss him not me yaoi fanfiction'. However, the availability can vary. Sometimes you need to dig a bit deeper and look through different tags and categories related to the anime and the yaoi genre.
You might have luck finding it on certain fan forums or manga-sharing communities, but again, make sure it's legal and doesn't violate copyright. Sometimes libraries also offer digital manga collections that you can access for free with a membership.
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.