The Plot Of Deltarune in a nutshell:

What's a " Deltarune"?

Interaction system was bombed by Afghanistan and wanted to commit suicide multiple times ... Red Lego monkeys brother is green Lego monkey and he left for collage to practice film study... Alex Spooky 1yr brother Salem died in a fire with 4 cousins... Toaa had a friend named Cheshire who practiced voodoo and spinels name is cooper and he lives in lake Elsinore We also know toaa saved Gabriel, Cheshire and spinel from suicide many times and that toaa was originally banned for defending spinel and his original OC was the executioner Gabriel went by the name " maby nobody will notice my pain to mask his suicidal thoughts as he broke up in a relationship with a girl

if you want me to read straight from the wikipedia page i will:

Deltarune is an episodic role-playing video game by American indie developer Toby Fox. Set in a parallel universe to his 2015 game, Undertale, the game follows Kris, a human teenager predetermined to save the world alongside Susie, a monster, and Ralsei, a prince from the Dark World. Throughout the story, the party establishes relationships with a variety of allies and opponents.

you should go watch an entire playthrough right now