Undertale: Trusting Oath is an Alternate Universe of Undertale where the monsters defeated the humans in the war and banished them to Mount Ebott in fear of them. This means that now, the monsters live on the surface happily, and humans starve underground. Characters in this AU also exist in the real life world, such as the Dreemurrs being replaced with the British royal family and Sans being replaced with the AU's creator. Obviously, the personalities and what they did are different from real life.
Story
It's March of 202X. You play as Monster Kid. You've heard rumors of mythical creatures called "humans" living underground while on the MonsterNet Forums. Intrigued, you decide to go explore Mount Ebott, but end up falling.
Characters
Monster Kid takes the role of Frisk
Noelle takes the role of Chara
Rose takes the role of Flowey
Camilla takes the role of Toriel
memesscience takes the role of Sans
River Person takes the role of Papyrus
Frisk takes the role of Monster Kid
Tom Stoltman takes the role of Undyne
Albert Einstein takes the role of Alphys
ChatGPT takes the role of Mettaton
Isaac Newton takes the role of W. D. Gaster
Charles III takes the role of Asgore
Prince Harry takes the role of Asriel