One possible plotline could be a moment of intense passion during a dangerous situation. For example, they might be in the middle of a battle against dark wizards, and Ron, fearing for Hermione's life, shows his love and protectiveness with that kiss on her neck. It could be a spur - of - the - moment thing that makes them realize their deep feelings for each other even more.
One place to find such fanfiction could be Archive of Our Own (AO3). There are many talented writers in the Harry Potter fandom who might have created stories with this scenario. You can search for relevant tags like 'Ron/Hermione' and 'kissing' to narrow down the results.
Hermione might be shocked at first. She has always seen Draco as an adversary, so a neck kiss from him would be completely unexpected. She could push him away immediately and demand an explanation.
In the fanfiction, Hermione's reaction would likely be shaped by her relationship with Fleur up to that point. If they have been friends, she might be a bit taken aback but then laugh it off as one of Fleur's eccentricities. However, if they have a more tenuous relationship, Hermione could become defensive. Her reaction might also be influenced by the presence of other characters. If they are in a public setting, she might be more embarrassed or try to quickly defuse the situation. And if there are underlying romantic or sexual undertones in the fanfiction, her reaction would be even more complex, perhaps blushing and feeling a bit flustered.
Well, it could be that the author of the fanfiction is exploring a more complex relationship between Fleur and Hermione. Maybe in this particular fanfiction's universe, there are different cultural or magical reasons for Fleur to kiss Hermione's neck. It could be a greeting in a certain magical culture they've created, or it could be related to a spell or charm that has some sort of connection to the neck area, and Fleur is using this as a way to interact with Hermione in a unique way.
Another reason could be related to a spell or a magical effect. There might be a love - inducing spell or some kind of magic that made Draco act in this way towards Hermione. The neck kiss could be the first physical manifestation of this magically influenced attraction.
In this fanfiction, it might be that Ami and Makoto are characters in a world where neck kisses have a special meaning. It could be a cultural or magical thing. Ami kisses Makoto's neck as a way to transfer some sort of power or energy to him, or it could be a way to mark him as special in their community's eyes.
One popular trope could be the 'forbidden love' trope. Maybe the characters are from different groups or have some sort of obstacle in their relationship, and the neck kiss is a moment of passion in the midst of that. Another could be the 'surprise moment' trope, where the neck kiss comes out of nowhere and catches the other character off - guard.
There could potentially be a fanfiction with that description. However, it's not a very common or mainstream concept. Fanfiction often explores unique and sometimes controversial relationships and situations. But this might be considered a bit out there, and it may be difficult to find unless you search through some less - regulated or more extreme fanfiction communities, which I don't really recommend as they may contain inappropriate content.
There are many platforms where you can find such fanfiction. Websites like Archive of Our Own (AO3) have a vast collection. You can search for relevant tags like 'neck kiss' along with the specific fandom you're interested in. For example, if it's a Harry Potter fanfiction, combine it with 'Harry Potter' in the search bar.