Another common theme is the exploration of their personalities. Writers might focus on yamada's more outgoing nature and miyamura's shyer side, and how these aspects interact in different situations. They could write about how yamada helps miyamura come out of his shell, or how miyamura's calmness affects yamada in certain scenarios. This can add depth to their relationship in the fanfic.
I'm not sure which specific 'Yamada My Love Story' you are referring to. There could be various stories with this name. It might be a personal story someone wrote, or perhaps a less - known piece of literature or film.