Kralsuselle

Kralsuselle is the poly ship between Kris, Ralsei, Susie and Noelle Holiday.

Chapter 1
During the majority of Chapter 1, Kris is the only one capable of interacting with all of Susie, Ralsei and Noelle. Susie starts out as Kris' bully, only to befriend them when they journey through their first Dark World in their school's storage closet together. Ralsei is a Darkner, unable to leave the Dark World, who guides Kris and later Susie on their journey. After returning to the Light World, Kris can talk to their childhood friend Noelle and find out that she has a crush on Susie. Due to the nature of Darkners and Noelle not entering the Dark World in the first chapter, Ralsei and Noelle don't get to interact with each other yet.

Chapter 2
The chapter starts with Susie dragging Kris towards the storage closet, finding out that their adventure yesterday wasn't a dream, but being interrupted by Noelle and Berdly telling them that they are at the library to work on their group project. Once Noelle is out of earshot, Susie opens the closet and she and Kris jump in, showing that the Dark World is indeed real. But when Ralsei comes to greet them again, he finds out that the two of them are procrastinating on their own group project and as Prince of the Dark, he regretfully orders them to go to the library to work on it.

However, when Susie wants to slack off again and opens the doors of the computer room of the library, they find darkness having turned the room into another Dark World. When they enter it, they find out that Noelle and Berdly were in the room while the fountain of darkness was opened, meaning that the ruler of the Cyber World, Queen, recruited Berdly in her quest to take over the world and took Noelle prisoner.

A fork in their path leads to Kris inevitably getting separated from Susie and Ralsei and leading right into meeting Noelle again. However, after Berdly and Queen independently make a truce with Kris to find Noelle (unaware that she's hiding right next to them), Noelle will ask Kris if they could also make a truce, joining them regardless as to what they say. On their way to navigate the city, the two of them can spot Ralsei and Susie happily eating cotton candy together, with Noelle being upset that Susie is "with someone", but also recognizing Asriel in Ralsei. Eventually, the two parties reunite, with Susie being initially reluctant to let Noelle join, as she believes that Noelle willingly helped Queen, but Kris and Ralsei welcome her. On their journey, Noelle will always unknowingly back out of fights, but is happy to help with puzzles. However, once they reach Queen's mansion to seal the fountain, Queen captures Kris, Susie and Noelle (along with Berdly), but forgetting to capture Ralsei since she ran out of cages.

Fanon
It was common to speculate that Noelle would become a main character after the release of Chapter 1, with her crush on Susie and unique text when deciding to name the vessel "Noelle" strongly hinting that she would become important. However, most of these scenarios involved her willingly going to the Dark World, either by seeing Kris and Susie sneak into the closet and following them or being invited by Susie under the impression that Susie was asking her out. Many Dark World designs of Noelle took inspiration of her being based on one of Santa's reindeers, often giving her a prominent red and green theme, but a sprite on Toby Fox's Twitter showed that her design was inspired by the Snow Queen instead.

The ship gained major steam after the release of Chapter 2, with fans wanting to stop the fighting between the Krusie, Kralsei, Kriselle, Suselle and Ralsusie factions. Though "Ralselle" does exist, many dislike it due to Noelle being all but stated to be lesbian, which is often reflected in the poly ship by having Ralsei and Noelle spend the least amount of time with each other out of the four. It is one of the few Kris/Susie/Ralsei combinations that are almost exclusively romantic.

Fandom

 * FAN FICTION