Shop NPCs are all the NPCs you interact with in order to create and train your dragon. Shop NPCs do not all strictly run shops, but rather, are the NPCs that inhabit the various locations you visit throughout Warm City.
A research trainee that greets you when you first go to the Research Center to create your dragon. Aside from giving you a tutorial on how the Research Center works when you make your first visit, which is entirely optional, Nina has no other role in the game except to greet you whenever you visit the Research Center.
The Head Researcher at the Research Center. Tomas will guide you through the creation of your dragon and comment on what he thinks of your dragon's initial stats and name. Guiding you through the creation of your dragon is Tomas' only role in the game.