The Ruler Of Darkness - Chapter 1Book 4:

His fiancée, whom he had never met, had just broken off their engagement. He's then betrayed by his girlfriend and schemed against by her lover.His mother's legacy awakens him. No longer content with mediocrity, he transforms into a dragon overnight.

[Moody Boy x Martial Arts Girl] [HE] [Male Lead is Crazy,]

Quan Zhisui didn’t understand why Wei Shixu was always getting beaten up by people from other schools, and why she constantly had to rush in to save him from danger. Later she found out that those people were just hired thugs.

They were paid by Wei Shixu.

“We’re through!” She firmly drew the line.

Wei Shixu smiled cheekily, “Fine, then don’t come to me for tutoring anymore. Fail the exam and repeat the grade, then let your scumbag dad and stepmom control you.”

Quan Zhisui had to compromise, “Let’s cooperate until the college entrance exam is over, but don’t go looking for trouble when there’s none.”

Wei Shixu: “I won’t go looking for trouble if you date me.”

Quan Zhisui: “I don’t date in high school.”

…

After the college entrance exam ended, Quan Zhisui went far away to university. She blocked all forms of contact with everyone, thinking that would make him give up his obsession, since it was decisive enough.

But she heard that at the awards ceremony, Wei Shixu tore up his university admission letter.

A year later, a certain repeater pursued her to her university.

In this world, orphans or just anyone without any hope for this world can apply to become a “walking target”. Their sole purpose is to be a practicing dummy for the students of the sect who train to become “Demon Hunters”. These students need “walking targets” to test their training on living, walking beings of flesh and blood.
In exchange, they will be provided with food & shelter.
Their existence value is lower than a slave, but if they manage to survive a few years they can receive a life long pension.

Xiao Han is such a “walking target”. One time he witnessed a powerful Demon Hunter disposing a demon. When the demon died, a fragment of the demon that managed to escape entered Xiao Han’s heart. No one saw that, and even Xiao Han himself only felt some discomfort for an instant.

But that thing in his heart soon gave Xiao Han visions, and the first one is of a cultivation method which allows Xiao Han to absorb damage to enhance his body. A perfect cultivation method for a “walking target”.

- Description from Novelupdates

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.