YO!!!!!!! I'm super excited cuz I'm pretty sure (XD) this is an original AU I made up, if it's not, then tell me who made it so I can give them credit for it. I don't particularly like stealing other people's ideas. Thanks! So, the AU is called Underdere where each person is a type of dere. If you don't know what a dere is then I'll tell you. A dere is a Japanese word for personality I'm pretty sure. For example, a deredere is a bubbly, eager, excited persona. I'll give you a list of what the deres I can think of mean;

Yandere- a mix of the words Yangire and deredere meaning they act sweet to their crush, but will secretly kill for them. They usually don't care who they hurt, as long as they get their Senpai.

Kuudere- someone who appears to be cold and sarcastic, void of emotions. The only way to unlock their emotions is to get them to warm up to you. They lack feelings so it's very hard to get them to warm up to you.

Oujidere- someone who appears arrogant, self-centered, full of themselves, and overall very snobby. They want to treated like royalty, especially by their crush. They think they are above everyone else, but really, they are just really insecure and don't want others to know, so they mask it by being like society, an *sshole.

Deredere- someone who is really bubbly, kind, sweet, and a really good friend. They are usually very innocent and rarely lie. They are also very loyal. They only ever act sort of shy around their crush.

Dandere- someone who is very shy and is often bullied. They get even shyer around their sanspai. They stutter a lot. They are often overlooked characters in anime for their shyness, but they are sometimes very brave in some situations.

Unidere- someone who is a mix of different deres. For example, a deredere and a dandere mixed together, a shy person at first, but as time goes on they become a very sweet and bubbly person around you, or a yandere and a oujidere mixed together, an *sshole who will kill for their Senpai.

Tsundere- someone who appears mean, rude, and cold, but secretly has a soft side. They are mainly mean to their crush and often puts their Senpai down and they are often in denial that they have a crush on their Senpai. They usually call everybody 'baka' meaning idiot in Japanese.

Those are the only ones I can remember rn but I'll add more as time goes on. I'm going to made a list of the characters and what dere they are. So, let's start;

Sans- Kuudere

Papyrus- Deredere

Toriel- Deredere

Asgore- Deredere

Alphys- Dandere

Undyne- Deredere

Mettaton- Oujidere

Frisk- Unidere(all of them except for Tsundere and Oujidere)

Chara- Yandere

Grilby- Kuudere

Muffet- Oujidere(not as much as Mettaton tho)

Monster Kid- Deredere

Napstablook- Dandere

Shyren- Dandere

Aaron(the buff seawhore- I mean, seahorse)- Oujidere

Flowey- Tsundere

Asriel- Deredere

Temmie- EXTREME Deredere

Tsundere Plane- Tsundere

Burgerpants- Tsundere

I'll also do Delta Rune too;

Kris- Kuudere

Susie- Tsundere

Ralsie- Unidere(Dandere and Deredere mix)

Roulx Kaard- Oujidere

Jevil- Deredere

Noelle- Unidere(Dandere and Deredere mix)

Berdly- Oujidere

Alright that's all for now! I hope you have a great day/night and if you didn't know, I love you! 💛