Son, “Mom” Will Back You - Chapter 1 & 2

A Count’s Daughter who lost in the running to become the Second Prince’s fianceé, Camilla. The Prince chose a Baron’s daughter as his fianceé, and the world blessed the two’s love as fated. On the other hand, Camilla who was tailored and elevated as the love’s villain in the end, as punishment she was made to marry a terribly fat and ugly man――called『Toad of the Swamp』from his appearance, a lord of a remote region named Alois.

I...AM...MOB CHARACTER!!!Sigh~My name is Samael, I was an office sla- I mean a worker who worked 9 to 5. It was a daily routine of monotony until one fateful day when I went home only to find my best friend with my girlfriend. Betrayal was the first thing I felt, followed by rage.And after taking ‘care’ of them, My surroundings changed…Looking at my reflection in a mirror, I noticed my appearance had changed. Gone was the face of the disgruntled office worker; instead, “SAMAEL ASHWOOD!!!” a character from a novel I used to read. But this wasn't just any character; I had become him—the sacrificial best friend of the protagonist who was betrayed and died in just the first two chapters.PROTAGONIST DIED!?[Heavenly Destiny System Initializing...][...]

“Everyone deserves a happy ending, don’t they?”…In the brutal fantasy RPG Fall of Ares, saving the world came at a cruel price — the deaths of every heroine the player had grown to love. No matter how skilled you were, their sacrifices were inevitable. The game warned you not to get attached.But one young man did.After beating the game and lamenting their tragic fates, he wakes up in its world — reborn as an extra, armed with one mission from a mysterious system:[Change their endings. Let them live.]Now enrolled at Mysteria Academy alongside the heroines doomed to die, he must rewrite fate itself. For every girl he saves, he’s rewarded. But the world resists change. Calamities draw closer. The true enemy — the Children of the Sky — are watching.And one of the heroines… remembers it all.

Witnessing her boyfriend cheating on her with her bestie, Shiyao was so angry that she went to a pub for fun and met a man, who was really a piece of work. After a crazy night she fled away, but was embarrassed to know that the man she slept with was her boss You Ze.
Jesus, give her a break!

- Description from Novelupdates