I have no idea how to make a story game. Like how do they force you to talk to an NPC?

Hopefully this won't get taken down. I have been wondering for the past couple of weeks how to create a story based game like Pokémon brick bronze ( I will not be using any copyright content or sprites)

For example how does it forces you to interact with NPCs, how when NPC moves into a new stage it stays there. How the NPC knows your username Once you see a cutsceen you can't re-see it and more Many examples but I can’t quite get my head around how they do it.

Help or examples will be appreciated! Thanks!