@beomgyu_yaoi,
But it was still a relationship, even if it was not built on love. They were expected to get married someday, or at least Claudia believed they would. Claudia accepted Matthias because she thought he could give her a more comfortable and secure life. She even gave up her true love for that future and prepared herself for it.
Even if love was not involved, plans and expectations still existed. It is not much different from many arranged marriages in Asian societies. Those marriages may have problems, and many people criticize them, but that still does not justify cheating or disrespecting a partner.
The same idea applies here. Matthias is still a cheater, and Layla has been pushed into the position of a mistress because their actions are still hurting another woman and trampling over the future she believed she had.

A cheating story written in the POV of the mistress. Idk why some people are romanticizing this, ts is pure slop. That Matthiass guy doesn't deserve a happy ending.