The 'best' can vary from person to person. However, fanfics that not only have the kiss but also build a believable relationship between Conan and Haibara before that are often more engaging. For example, those that explore their shared experiences in the face of danger and how that deepens their connection before the romantic moment. You can start by looking at the most popular ones on platforms and then see if they suit your taste.
There are no definitive 'best' Conan and Haibara kiss fanfics. But you could search for fanfics that are written by experienced writers. They might be more skilled at creating a realistic and interesting scenario for the kiss. Also, fanfics that incorporate elements from the original story, like the mystery - solving aspect, along with the relationship development between Conan and Haibara, can be really good. Try to read a few samples from different fanfics to determine which ones you like the best.
Chapter 104, "Camp Strength, Rapid Enhancement (2-in-1 Large Chapter)", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. Early on, Opening the camp system interface and seeing the data on Wood, Coal,.... By the end, Wood, of course, is not a problem, but 5000 units of iron mean even....
Chapter 134, "Difficult Hunt [Warm Sun Tycoon Extra 3/10]", is the clearest early answer because the buildup finally cashes out in a real clash. The setup is Long defense will inevitably lead to loss, especially when mobility..., but the pressure keeps building through Soon, Snow Mane's head was once again pierced by hundreds of iron....
Chapter 211, "Elite System, Mining, and Cheng Ping's Grudge", is the clearest early answer because it turns Cheng Ping's situation into a concrete plot event. It opens with The two swords on Xia Hong's back were actually quite noticeable. and closes on Do you think I don't dare to kill you?" "I mean no such thing, just.... The key payoff is that it gives power growth practical battlefield or strategic value, making the technology side of the story feel consequential rather than decorative.
Chapter 175, "Ape Mountain, Xiao He Camp", is the clearest early answer because it turns Xiao Daoyin's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Hearing Xiao Yuan's recounting, both Xiao Yu and Xiao Hen turned... and follows through with This was not what he had anticipated!.
Chapter 118, "Poison Sac, Bow Making [2 in 1]", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. The chapter gives readers a real answer by opening on This number, although large, is actually not unattainable. and ending on There should still be a bit more at the mine; I'll first mass-produce....
Chapter 121, "Ready for Everything, Time to Take Action [Three in One]", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. It opens with After Xia Hong finished speaking, he gestured for Xia Chuan to rest... and closes on The front row was all holding longbows, carrying arrow quivers..
Chapter 155, "Lone Ranger, Xinggu Pass", is the clearest early answer because it pushes Intermediate Cold Beasts into a new phase or setting. A useful checkpoint is the way the scene starts with First Year of the Great Xia, March 7th Six kilometers south from the... and follows through with Of course, the most crucial thing was what Xia Hong learned from Gao....
Chapter 178, "Reciprocal Meeting and Big Moves", is the clearest early answer because it turns Xiao Ning's situation into a concrete plot event. It opens with That's true, after all, Xia Chuan was just a passing acquaintance. and closes on The content of the three men's words undoubtedly added to their heavy.... The key payoff is that the chapter closes with Seeing Xiao Kangcheng's cautious inquiry, Xia Chuan sighed internally but quickly put on a smile.
Chapter 115, "New Earth-digging Realm, Enhanced Mining Efficiency【Three in One】", is the clearest early answer because Yuan Cheng finally turns buildup into a real advancement. Early on, Big brother, this giant axe is for hunting the Teng Jiao, right?".... By the end, Part of why he had been trying hard to break through to the.... Inside the broader power growth storyline, the chapter closes with "Definitely higher than theirs, but we don't know the specific distribution yet.
Chapter 185, "New Home, Land, Arrow Bamboo Forest", is the clearest early answer because the buildup finally cashes out in a real clash. It opens with This number is really too tempting! and closes on While doing so, let's see if there's any other human camp on the....