There are several places. AO3 is a great start as it has a well - organized tagging system for easy searching. Wattpad might also have some kyo x yuki fanfiction. Some smaller, niche fanfiction communities dedicated to the source material of Kyo and Yuki might also be a good place to look. Just make sure to follow the community rules when exploring these sites.
You can try some popular fanfiction websites like Archive of Our Own (AO3). It has a large collection of different fanfictions, and you're likely to find a good number of kyo x yuki ones there. Another option is FanFiction.net.
AO3 is probably the best bet. It not only has a vast amount of kyo x yuki fanfiction but also allows for various filters to help you find exactly what you're looking for. You can filter by rating, word count, and more. FanFiction.net is also a classic place to search. And don't forget about Tumblr. Some Tumblr blogs might share or even write their own kyo x yuki fanfiction, although it might be a bit more scattered compared to the dedicated fanfiction sites.
If you want the clearest chapter reference, go to Chapter 11. Early on, After a meeting, Shang Shaojing pinched the bridge of his nose, tired, and...; later, the chapter leans on How is it going with the Jiang Family?" The assistant looked troubled and....
Chapter 778, "The Gift of Being a Director", is the clearest early answer because it turns Shen Lan's situation into a concrete plot event. The chapter turns that into something concrete by moving from Shiguang, I really misjudged you, you're actually this kind of...
Look to Chapter 31 for the clearest answer. It begins with Before Shen Lan had reached the backyard, she already heard the sounds of..., keeps building through Facing the freshly risen morning sun, she noticed at a glance the girl..., and lands on After staying in the study and reading for another.
Chapter 781, "Master, accept my bow!", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Not only were the criminals curious, but so were the others.
Chapter 756, "Birthday Banquet", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. The chapter turns that into something concrete by moving from On the day of the birthday celebration, the Jiang Family got up early.
Chapter 826, "Deadlock", is the clearest early answer because the violence around Shuiyun Temple becomes final instead of hypothetical.
The best chapter pointer here is Chapter 37, "Those in the know anticipate the transformation, while the oblivious think it's a fashion show.". It opens with The barrage was suddenly filled with hahas, but the two guests present...
A practical answer is Chapter 13, because it turns the idea into a concrete scene. The chapter opens with Sensing that something was off with Jiang Yan, Jiang Yan dismissed the..., adds pressure through He probably had a good guess who it was., and ends on How could this happen..." Lin Manru.
Chapter 920, "College Entrance Exam Results Inquiry", is the clearest early answer because it turns Meng Xuezhi's situation into a concrete plot event. Early on, Outside the nursing home, Meng WanZhi anxiously waited in the car for....
Chapter 709, "But He Really Is My Second Uncle", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter turns that into something concrete by moving from The voice came from Jiang Li.