Check Mark
This page has been brought up to standards by an Admin/Bureaucrat, and now checks out. Please try not to mess it up.
* To know more, see:


SideHeart is an AU of Undertale where a human falls before Chara, all of the humans are still alive to this day, and a civil war takes place.

In the world of SidesHeart, a civil war took place, and a great battle between the factions of Undyne and Asgore, who perished, led to a rather tense situation nowadays. Actually the war happened because the Dreemurs wanted to spare the fallens humans, thus they'll never break the barrier. In a very differrent Underground, where all the humans are alive and grown up, two rivals kingdoms emerged and a child with a unique soul fell before Chara,

Frisk fall at his turn. What will happens next, no one knows for sure right now.


Undertale Characters

  • Toriel : She's now the leader of the Royal side, since her husband was killed in the great battle. She's taking her job seriously, and is known for her protective and caring nature, especially towards humans.
  • Undyne : The leader of the Rebel side, and former general of the army. A very powerful and skilled fighter, without any pity to mankind. She's still in love with Alphys. After the great battle, she was exiled in Waterfall, where she now prepares a counter-attack.
  • Papyrus : No longer the innocent sentry in Snowdin. During the war, he became the new general of the Royal Guard, and is probably the second most skilled fighter of the Underground. Distant, ruthless but still friendly in some ways, he's especially fond of the Bravery soul. Along with his brother, he was created by Gaster and the first fallen.
  • Sans : Now the Royal Scientist, since Alphys flew with her lover. Really intelligent, but very recluse and a bit aggresive, he rarely talks with peoples outside of his close circle. He had to leave his brother in Snowdin before reaching Hotlands. Still enjoys puns, but on a more dark and sarcastic side. Along with his brother, he was created by Gaster and the first fallen, his best friend now.
  • Alphys : Flew to Waterfall in order to follow her lover. Nicknamed as the "Rebel scientist", she's still very clever, and created a whole new lab in Waterfall. Less shy than before, but not a bad person. Secretly, she hopes a peace agreement will be found in the near future. But for now, she's still creating deadly machines.
  • Metatton : A traitor in disguise, is pretending to be in the Royal side. Still perfoming his shows at the MTT resort, and still very vain. He was upgraded by Alphys to be more deadly before her escape, and now posseses a chainsaw hand in his EX form. Only waiting for a signal of her boss Undyne for one last ultime perfomance...
  • Muffet : She never clearly took a side in the war, and remained at her bakery sales. But Undyne bought her with money, and she might be a formidable opponent to any challenger. Still the same in personality, although she doesn't enjoy cider, but wine.
  • Napstablook : Probably the less changed character, they only want to be alone. Now lives exclusively in the Ruins, because the rebels destroyed his house (even if Undyne was against).
  • Chara : The same as the classic one for the most. The rivalry between her and the first fallen for Asriel's frienship was a big gap in the Dreemur Family, even until her death.
  • Asriel/Flowey : Globally the same, couldn't choose between his two siblings. After his death, he reborned in the form of a orange and black flower, in the same flowerbed where he past away.
  • Frisk : Exactly the same, only he's confirmed to be male.
  • Asgore : The former king who spared the fallens humans. He was nice and caring, like his wife. Deacesed in the great battle, presumably by Undyne.
  • Gaster : The first Royal Scientist. He became the teacher of the first fallen, and together created the skeletons brothers. Was very intelligent, but also hot-blooded, he died when he fell to his doom in the CORE.*
  • Gerson : The old turtle vowed his life to Undyne, and he's one of the main soldiers. Very brave, but his age prevents him from participing in too many skirmishes.

Added Characters

  • Celeste ( Patience ) : The first of the 6 fallens, and the more mature. She has the physic of a woman in her thirties. Caring, gentle and possesive, she's like a humanified Toriel, she's even the current caretaker of the Ruins. Is the older sister of the Justice soul.
  • Brayan ( Bravery ) : Currently lives in Snowdin, and fought during the great war. Audacious but impulsive and hot headed, he's best friend with Papyrus. Celeste raised him since his childhood. Never lost a fight, but not as skilled as his skeleton friend.
  • Aurelia ( Integrity ) : Sentry at the border Snowdin-Waterfall. She lives a hermit lifestyle, even though she's in a romantic relationship with the Kindness soul. Dances the ballet with perfection, she never takes off her tutu. Kind, but can be deadly serious if needed, Aurelia never lies.
  • Pam ( Perseverance ) : Is helping Sans in Hotlands's lab. One can thinks of her as the archetype of the nerd, shy and reserved. Despite her obvious crush on her "boss", he's completly oblivious to her feelings. Can be very efficient and perserverant, but also very selfish.
  • Rory ( Kindness ) : The first spy of the queen, and also a true gourmet with food. Has two sets of outfits, for each job. Engaged in a romance with Aurelia, he's also the best friend of the Justice soul. Despite having the kindness trait, he's serious almost at all time, somes might even say he's emotionless.
  • Jade ( Justice ) : The youngest of the 6, physically not even twenty. Always in the front of a threat, and dislikes lie, she's always willing to help and comfort anyone in need. Best friend with Rory and younger sister of Celeste, they stay in touch. Usually fight with a true pistol.
  • Josh ( Pure Determination ) : The first fallen and first prince. Had a rivalry with Chara for the sake of Asriel's friendship. He created the skelebros with his friend and tutor Gaster. Has a very powerful and unique soul, even though he cannot erased nor save, he stills can remember timelines. Now, he's roaming the Underground, alone most of the time. But this alone man deeply cares about the monsterkind, even the ennemies, and would do anything to stop a monster rampage.


Undertale locations

  • Ruins : Mostly the same, inhabited by Celeste and Napstablook notably. The amount of monsters in the zone decreased through time, since most of them went to the nearby Snowdin. A huge portion fall in decay.
  • Snowdin woods : Around the city, woods are filling most of the space. Rebels sometimes ventures in there, so one must be cautious. One notable location here is the memorial in memory of Asgore.
  • Snowdin town : Now a rather well fortified border town, and the news headquarters of the Royal Guard. The population in the city is around 2.000 persons, making it the second most populated area. Papyrus and Brayan reside here.
  • Border : The small zone between the town and the first caves. Inhabited by Aurelia.
  • Waterfall : This area is fully occupied by the rebels, since they were exiled here. Since the beggining of the caves to the entrance for Hotlands. Here, any royalist must be very carefully. A magical barrier prevents most of the potential attacks, but lately it is getting old.
  • Hotlands : Mostly consisting of lava and magma, the only notable place is the lab, where Sans and Pam reside and work.
  • New home : Still the capital to this day, and home of the Royal H.Q. Heavily defended and fortified in case. Most of the monsterkind lives here. Jade resides here.
  • Royal mansion : The home of Toriel and Josh. The last corridor is included in its basement, leading to the garden room.
  • Garden room : Former Throne room, where Toriel can be found most of time, taking care of a bunch of daisies. The throne was threw away after the death of Asgore, and this became a little sanctuary of quietness.
  • Barrier room : The said barried is still very present, and nothing had destroyed it to this day.

Added locations

  • Asgore Memorial : Somewhere around Snowdin town, in a little clearing, a wanderer can found a statue in the memory of Asgore. Each month, some golden flowers are planted in a few pots around the sculpture.
  • Freedom town : Undyne and her folks built an entire new town, where before was standing her house. Around 2.600 persons live here, and the position is heavily fortified. Here can be found the rebel H.Q and the New Lab.
  • Beruhmtheit : The last floor of Hotlands and the CORE have been renamed in order to form only one entity. A few hundreds monsters dwell here. The area is recognizable to his technological and futuristic decoration, Metatton redid everything. The MTT resort is included. The most importants residents are Metatton, Muffet and Rory.


  • A soul, the Pure Determination, has been added.
  • The final boss fight is replaced by the Pure Determination soul.
  • The theory of Gaster creating Sans and Papyrus is canon.
  • Frisk is masculine and Chara feminine confirmed.
  • Alphys x Undyne is still confirmed.


Firsts Events

A long time ago, years after monsters were trapped undergound, a human fell. He was hurt, but alive and, called for help. Asriel, son of the king, came to his rescue. His name was Josh.

He was adopted by the Dreemurr family, and all the underground lived peacefully.

Until the day another human fell, and Asriel helped them too. Their name was Chara. They became closer, way closer than Asriel and Josh, which brought some hate and jealousy inside Josh.

Everything was alright, until Josh had enough and challenged the other human. It's with a legendary calm than the human accepted, their fight will take place the next day.

Despite the efforts of Asriel too stoped it, the fight took place. Having worked under the tutelage of gaster and having gaining much magics powers, Josh should have had the advantage but strangely, the more the fight progressed, the more Josh had doubts his opponent was really human.

He emitted a strange energy, Josh didn't know what it was, but he prefered fight for his honor. His rival not having moved yet, took out a sharp knife and run into him. One hit and Josh was down with just a few HP. Chara get closer, looking like to finish him, but instead they helped him to get up and said :

"Humans are weak..."

And he returned to Asriel.

Everything was alright again, until the tragic day were Chara andAsriel died. The Dreemurr and the entire kingdom cried, but Josh didn't cried. He smiled. It was a smile of hate.

After those funerals, the king and queen have too take a important decision. Should the humans be killed knowing one of them live among monsterkind ? A long debate started between them and quickly escalated into a verbal fight. Josh stopped it, he became cold and distant when his sibling died, but when the debate took serious measures, he calmed it and the decision was took. Fallen humans will still be protected by monsters.

Several others humans fell, but some monsters, as Undyne, really disliked the policy of the king which favorised the ones who made their ancestors suffered so much. She decided to start a rebellion with the fellow dislikers monsters against the Dreemur.

War was stated.The two factions, loyalist and deviant, fought against each others without mercy. Many monsters died for their leaders. During the battle, Undyne killed Asgore. The rebels were still beaten with the helped of Sans,Gaster and Josh.The three of them created a magic barrier between Waterfall and the rest of the kingdom, Waterfall where the rest of the deviant monsters were banished and where they built another city, in the waiting of their revenge.Their ultime goal is to destroy the barrier.

During this period, many were the traitors, spies and assassins. The Underground must be saved from this situation, but by who ?

New Era (Pacifist Version)

After the firsts events, Frisk, a young human, fell into the Undergrond, into the Ruins. He first met with Flowey, but is saved by Celeste, the patience Soul. Together, they travelled into the Ruins, and they finally arrived at Toriel house, now the human's one, where she told him more about the lore. But a rebel broke into the house, thus forcing Frisk to flee to Snowdin, leaving the fate of Celeste unknown.

At Snowdin, now a rather well-fortified town, the young human met with Papyrus, the Royal Guard leader and Brayan, the Bravery Soul. Frisk is then informed about the war and the situation in the Underground, learning that Undyne and her clan is confined into Waterfall. But since Frisk wanted to go further, both Papyrus and Brayan escorted him to the edge of Waterfall, where all three met the sentinel of the edge and the Integrity soul, Aurelia.

She told them that the situation is complicated, Undyne's troops kept attacking lately, but is confident about Frisk demise, this one being accompanied by two strong persons. She also thought Frisk might be the one who'll reunite the two clans, and will break the barrier. After a moment of discussion, she let them go away into the enemy territory.

Quickly, they fought Alphys and many of the Rebels troops, and at a time Frisk was separated from his friends, and get lost. After a moment of alone walk, he found the Rebel H.Q, and town actually, named Freedom. He crossed the town without any injuries, but Undyne was waiting for him at the eastern edge of Waterfall, and they fought. The fight was tough, but the human won, and spared Undyne, before travelling furthermore, and reaching Hotlands.

He then came across Sans, now the Royal Scientist, and his assistant, the Perseverance Soul, Pam. The skeleton told Papyrus the human was alright, and explained more about the creation of the magical border, and the first Royal Scientist and his creator, Gaster. He also saw in Frisk the savior of mosnterkind, but was interrupted by Mettaton, who launched his quizz as usual.

The journey through Hotlands was without many interruptions, other than Mettaton games, solved with the help of Sans. But when Frisk reached the end of the area, he met with Muffet, who fought him. During the fight, she told she's neutral, and only doing it because of money, Undyne paid her, and doesn't really care about who she's working for. She then let Frisk went away, and disappeared into the darkness.

Frisk reached to MTT Hotel, and had a dinner with Sans. He then discussed about the Prince Josh, and how he was his creator too and they had a brotherly-like relationship. Also, he told him to be careful here, the spies are everywhere. Frisk also met with the Kindness Soul and royal spy, Rory ,who warned him about Mettaton strange behavior.

Frisk followed his advices, and entered the CORE, and had to fought many mercenaries, and MTT himself, who reaveled his betrayal on TV live, in front of more than 10 000 viewers. After reaceving phone calls about how he will miss everyone, on both sides, he decided to spare the human, and deactived himself; Frisk was then free to go.

The human took an elevator to the Capital New Home, where he went through Toriel house, and learned even more about the first events, in particuliar how the soul of Josh was unique, and way more powerfull than everyone might think about. He also met the last fallen soul, the Justice Soul named Jade, who narrated the fall of Josh, and the events of the first war, implying the death of Asgore.

After Jade left, the young human Frisk entered the last corridor, where he faced with Josh in person, the judge and Pure Determination Soul. Josh told how Frisk actually saved the monsterkind, since after her defeat, Undyne accepted to sign a peace agreement, and is actually discussing with Toriel in the next room. Josh accompanied Frisk to his adoptive mother, who wasn't in the Throne room, but in the Barrier room, with Undyne, Alphys, Papyrus and Sans.

Everyone was happy to see Frisk again, including the formers rebels, and the peace agreement was signed. But then Sans asked about the break of the barrier, and before someone could say something, a creeped came across and imprisoned everybody in the room, excepting Frisk.

Flowey emerged from the ground, and mocked Frisk about how he wanted this 'happy ending", and started attacking with his pellets. But soon the human was protected by everyone, and the entire Underground was reunited against Flowey in the Barrier room, cheering on Frisk. Eventually, Flowey got bored and changed into his true form, using all the souls he could gathered, even humans ones , Asriel God of Hyperdeath, and mocked Frisk , stating he didn't has any chances to defeat him, and the fight begun.

During the fight, it was obvious Asriel mistook Frisk for Chara, but never realized,as he made many references to Chara's life. He changed into his final form, the more powerful he could be. But Frisk, with his determination, managed to save the souls of his friends, and even Asriel's one.

Asriel being saved, the goat child accepted to free the souls, thus breaking the Barrier, before going away. Frisk woke up into the Barrier room, circled by all of his friends. Everyone was relieved, and happy they were free, and the monsterkind being saved. Then, they moved outside, facing a dawn sun, and they began their new life, among the humans.