Short Story: Soulmates

MC bumps into the Dark Lord and upon contact they exchange thoughts and realise that they are each other's soulmate and that they had both decided to get rid of their soulmate when they would encounter them.

The world

Society

This world has a society similar to 19th century France, with mages who duel to solve problems and debates.
There are different "schools" of magic with each a lord at its head. Those "lords" have followers and advocate for their schools. Each lord's fellowship works like a mixture between a guild and a loose family. They can get very big, but the core members (i.e., the masters and politicians) all recognise each other's names at least.

Politics

The Light and Dark lords have a big rivalry, although this is not an open war (yet):

The Dark lord is the lord of the most dangerous type of magic, mostly centered around rituals. This is made of a combination of symbolic magic and magic coming from the environment rather than internally, and so it does not have very strict rules and is difficult to control and dangerous, but it's also very powerful and has an incredible potential.

The light lord is the lord of runic magic, a type of magic made with lots of mathematical calculations, and so this is fixed magic which always has a defined outcome. This magic also allows for building up on previous inventions to make artefacts that are more and more complicated and powerful.

Soulmates

People have soulmates, individuals whose magic have the same wavelength. This allows soulmates to create a powerful magical bond together to then exchange magic, communicate mentally and combine their magic in extremely powerful displays. Soulmates are very rare but not unique. Despite this, they are considered to be very romantic and there are strong social and legal expectations that soulmates are going to marry no matter who they are, their age, gender, or marital status (they will just have to divorce any previous spouse).

The character

MC

Who she is: MC is a follower of the light lord and is a mathematician who makes calculations that are then used in the production of artefacts.
Character: She values her independence extremely highly. She likes being respected and to receive aknwoledgement for her status, and so she got a math mastery. However, she absolutely refuse to have anyone watch over what she is doing and profess their opinion and try to interfere. Because of this, she stays away from politics and never express her many controversial opinions in public or what she thinks about the people around her.
She is considered like a nice shy girl and to be talented but inconsequential, and that is exactly what she wants.
Soulmates: She absolutely hate the idea of soulmates and has long decided to get rid of her soulmates rather than be forced to marry them. Obviously, the dark lord is not just someone she can assassinate... In addition, being the dark lord's soulmate thrusts her in the center of politics, and she is very angry about it.

The Dark Lord

Character: He wants total freedom and independence from everyone. He grew up poor, depending on people's charity, and with a controlling family, and his independence was hard fought over.
Politics: He thinks that all magics should be legal and that people should only be held responsible for the acts (e.g., killing someone) rather than for the magic itself. He does not care if people get killed along the way because of magic they cannot control; they are all adults responsible for their own decision and aware of their own limits and of the risks they are taking, and so it is their own problem if they want to kill themselves.
He is however for the reinforcement of punctual wards over the city to protect from out-of-control rituals to avoid everyone getting killed as soon as an idiot attempts a ritual they cannot control.
Soulmates: He hates the idea of soulmates and being forced to bear the presence of someone weaker than him, let alone marry them.

The light lord

Character: He is a genuinely nice old man who always try to do what he thinks is best and most moral and to help people. Unfortunately, he is also very arrogant and self-righteous without being willing to acknowledge that, and can be very judgmental and stuck in his way. He is both very nice to be around (when he likes you) and also very frustrating and infuriating.
Politics: His goal is to better society, and for him this goes through getting rid of the dark lord who is advertising a very dangerous magic and making it look attractive, thus putting everyone in danger.