Ghoultale is a crossover AU between Tokyo Ghoul (which I do not claim to own!) and Undertale. In it, the main protagonist is still Frisk but they are the seventh half-ghoul to be created and dropped down Mt. Ebott after an experiment involving the first human to fall, Chara, and the son of the most powerful ghouls named Asriel, failed and turned into a powerful, although unstable, ghoul that is referred to as "Rize".
GhoulTale is generally based off the routes, but the Neutral Route is much harder to get since you must perfectly balance how many characters you kill/eat and how many you salvage. Kill more, you get a Genocidal Route and will end the story with kakuja abilities. Save more, you will end up bringing humans and ghouls together. You cannot save everyone, as being a half ghoul you depend on killing to eat.
Frisk replaces the role of Kaneki and after an unauthorized surgical implant turning them half ghoul, they are dropped down the mountain as another one of humanity's attempts to destroy all ghoul life, much like the CCG. The ghouls, who are also monsters (meaning, they look the same but have kagune and kakugan), have been seeking revenge on the humans for locking them up and only getting the odd tourist group of food to fall down the mountain. However, they have turned on one another and through careful sprees keep their population down without destroying it entirely.
So, from the very beginning, a war broke out between the races, and the humans won, banishing the monsters below ground. One day a human fell down and met Asriel, where they formed Rize and were captured by humans to make half ghouls, bent on eliminating the monsters. The first six fell and were eventually captured to destroy the barrier when enough humans were collected, and the seventh one, Frisk, is different for one reason. They are determined and can reset their progress through the timelines, saving themself from dying to move forward.
As of now; separate character pages may be made later.
Frisk --> Kaneki Ken
Chara --> Rize Kamishiro
Flowey --> Kishou Arima
Toriel --> Touka Kirishima
Napstablook --> Hinami Fueguchi
Sans --> Nishiki Nishio
Papyrus --> Nishiki's elder sister *
Grillby --> Yoshimura
Undyne --> Kuki Urie **
Alphys --> Ginshi Shirazu **
Muffet --> Uta
Mettaton --> Ryoko Fueguchi
Temmie --> Juuzou Suzuya
Gaster --> Eto Yoshimura ***
Asgore --> Shuu Tsukiyama ****
Asriel Dreemurr --> Hideyoshi Nagachika *****
* : Obviously, not only is Papyrus alive, but also male and younger
** : So these two characters are in fact Quinx, after Alphys did some scientific work on it. So they started as regular monsters with kagune and Alphys replaced both hers and Undyne's with more personality-specific built in quinqu
*** : Obviously Gaster is only Eto and not the author as well.
**** : Because who doesn't love a potential pedophile as a king? Mostly this is due to the Tsukiyama wealth and power in Tokyo; Not Shuu's individual personality.
***** : Because Frisk and Asriel are best friends, no?
Obviously all characters are simply somewhat related to their Tokyo Ghoul counterparts and are in no way complete copies. Genders and appearances are unique to the Undertale characters, although kagune and quinque are not.