Deltarune

Deltarune (stylized as DELTARUNE or deltarune) is an in-dev computer game by Toby Fox. Chapter 1 was released October 31, 2018, with Chapter two following on September 17, 2021. More chapters have been announced, but according to Fox, there has been "0%!!!" work done on the actual game, however, the story and some songs have been completed.

The story so far follows Kris, the silent controllable protagonist, and Susie, a violent monster, living in Hometown. The not-so-ideal duo at first stumble upon a "Dark World" inside their school's storage closet, and meet Ralsei- an Asriel lookalike who joins the party on their quest to seal a Dark Fountain that can cause damage to the world.

Trivia

 * While it consists of chapters, Toby Fox has stated it won't be released chapter by chapter.
 * Despite the confirmation that Deltarune was indeed an AU of Undertale, it has also been suggested that there may be connections between the two games.