Undertime is an AU where the main character Sans and the Narrator try to uncover the mystery around the disappearance of the residents of the Undertime universe. There is one crossover to the AU Horrortale, which i do not own, none of the characters are mentioned or used but the universe is used slightly. Also the mention of Ink Sans and Error Sans, which i do not own, they are not present in the story but it should be mentioned. All credit goes to its rightful owners, i own the Undertime universe and characters accept the ones mentioned above. 

Inktale owned by Comyet 

Errortale owned by TheCrayonQueen 

Horrortale owned by Sour-Apple Studios