Natsu is the central figure for sure. His parents are the key characters he's going to meet. But there could also be some side characters from his guild. For example, the guild master might have some information about Natsu's parents and be involved in the meeting somehow. And maybe some of the older members of the guild who knew Natsu's parents in the past.
Obviously, Natsu himself would be one of the main characters. His parents, whose identities are likely to be revealed in the fanfiction. There could also be his friends, like Lucy, Gray and Erza. They might be there to support Natsu during this emotional encounter or play a role in helping him find his parents.
A practical answer is Chapter 113, because it turns the idea into a concrete scene. The chapter opens with The next day, Jiang Lili was up before dawn as usual., adds pressure through Okay, keep them steady;
The best chapter pointer here is Chapter 113, "Morning Exercise Check-in Group!". It opens with The next day, Jiang Lili was up before dawn as usual. and closes on If things are really as you say, that is indeed quite serious..
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.
A practical answer is Chapter 112, because it turns the idea into a concrete scene. The chapter opens with These five people are supposed to be at odds., adds pressure through Do you remember that bowl of Mushroom Soup?" Jiang Li smiled, "Your..., and ends on [Hahahaha why is the Princess starting.
If you want the clearest chapter reference, go to Chapter 154. Early on, Hahaha, I'm dying of laughter, Lili, do you really have to be so blunt?"...; later, the chapter leans on His expression is killing me!!!" "Help, she's making a scene, he's....
A practical answer is Chapter 132, because it turns the idea into a concrete scene. The chapter opens with The new girl in the live-streaming room went crazy., adds pressure through Stay away from my fragrant and fresh Brother Daniu!] [Not only has the..., and ends on He stir-fried the other.
If you want the clearest chapter reference, go to Chapter 123. Early on, After He Yun also carefully rolled up her trouser legs and walked down...; later, the chapter leans on [Jiang Li, why are you still wandering around the edge?.
Chapter 116 is the strongest chapter-level answer because it starts from But before the audience in the live room had time to continue brewing the... and follows through on Their old Jiang family never had such twisted genes in hundreds of years!.
Look to Chapter 142 for the clearest answer. It begins with The ingredients for making Buddha Jumps Over the Wall were still on their..., keeps building through There were so many people in the village, just making a small portion was..., and lands on Wen Jiaojiao immediately lit up and stepped.
If you want the clearest chapter reference, go to Chapter 144. Early on, Ordinary people would have been at a loss in this situation by now.; later, the chapter leans on But Jiang Yan was, after all, Jiang Yan..