I'm not going to say you should form new chapters centered around developing trust for every single Pokemon some trainer will have, because it'll get a bit too formulaic and predictable along with slightly boring. I don't advocate setting aside character-development chapters for that many Pokemon. It would be better to gain trust while going on their journey. Maybe trust can spark from a random event, but I still think it should gradually be built on. In my honest opinion, I find it far more entertaining to read stories that move the plot along while having characters develop in the process, because that's pretty much the point of the plot in character-driven story.
My point is that it's fine to have chapters specifically written for character development, but having like six chapters just for Pokemon to trust their trainer is a bit excessive. I'd tone it down, but the idea is fine.