To develop their relationship in a fanfiction, you could start with Hei being more protective of Yin. As the story progresses, Yin could start to understand Hei's motives better. Maybe they get separated for a while and when they are reunited, they realize how much they mean to each other. You can also introduce other characters who either support or oppose their relationship, which would force them to define their relationship more clearly.
Their relationship can be developed by having them share more personal experiences. For example, they could talk about their past traumas and how they've coped. This would create a deeper emotional connection.
If you want the clearest chapter reference, go to Chapter 179. Early on, Everyone originally had no expectations for the gifts that Su Yinwan...; later, the chapter leans on Although they felt there might be a catch, a few people still curiously....
A practical answer is Chapter 153, because it turns the idea into a concrete scene. The chapter opens with Wisps of smoke gradually rose from the small kitchen., adds pressure through But the next second, Jiang Li looked up, with a sincere face she said,..., and ends on After leaning in, he saw.
Chapter 163 is the strongest chapter-level answer because it starts from Su Yinwan entered a small room, guided by a staff member. and follows through on Moreover, by doing so, the online viewers would think her more innocent....
Chapter 190 is the strongest chapter-level answer because it starts from Several people who didn't understand fell silent. and follows through on Because he saw the pack of cigarettes pinched between Jiang Li's fingers..
Chapter 159 is the strongest chapter-level answer because it starts from Seeing the red light of the camera turn on, Su Yinwan looked at the... and follows through on Shang Shaobai, who was browsing through files, received a call from his....
The best chapter pointer here is Chapter 126, "The Production Team Actually Played Dirty on This?!". It opens with Wen Jiaojiao initially wanted to cause trouble. and closes on The trolls lurking in the live stream immediately seized the opportunity....
A practical answer is Chapter 169, because it turns the idea into a concrete scene. The chapter opens with Everyone: "What?!" Seeing the shocked and bewildered expressions on their..., adds pressure through If you signed up, be ready mentally.] [Exactly, supporting the sister..., and ends on Wen.
A practical answer is Chapter 146, because it turns the idea into a concrete scene. The chapter opens with Director Sun: "???" Jiang Li smiled and said, "In the past, the show crew..., adds pressure through Otherwise, if they hog all the spotlight, what will we do?, and ends on That way, they.