Deltarune is the second Tobyfox’s project featuring familiar monsters. Though the plot unveils on the surface, and Toriel actually works as a school teacher, it has little connection to Undertale. It is more like an alternative dimension that shows us a rearranged screenplay with the same actors.
It has a lot of references to the first game, so a fan will have a great time laughing at insider jokes. However, the planned seven chapters have their individual depth. A player can estimate the idea without being acquainted with Frisk’s story.