Toaru Kagaku no Railgun SS - Volume 2, Chapter 2

After being kicked out by her family, she turned out the real heiress worth billions, and people around her got to know it.Her family regretted deeply and demanded half of her fortune as repayment for bringing her up. She sneered and used a truth-telling talisman to expose their plots.A scumbag had always been pestering her and wanted to get back together. She easily made him “meet his ancestors” every night.Moreover, her cousins had looked down on her, regarding her as a disgrace.Surprisingly, the chairman of a rich family came to her and said, “As long as you can save my daughter, I'll meet all your demands!”Another rich family, who had been at feud with her new family for a long time, also shamelessly came over and said, “As long as you can help us, our family will be very grateful for the kindness of your family!”Later, even the rebellious cousin became her follower, claiming, “She is my only sister! Whoever dares to insult her, I will curse their entire family!”Her new family finally realized that their little poor girl was actually a big shot!“I need to draw spells, get rid of evils, save people and chase that guy! How busy I am!” She said in distress.That guy, “Actually, you don't need to chase me. I'm already yours.”

Su Yan adored Xie Yu for many years and finally got what she wanted, but Xie Yu ran away on the wedding day, making her a laughing stock. At that time, Bai Xingfan appeared in front of her. He held a black umbrella in his skeletal hand to shield her from the heavy rain, and the other hand stretched out in front of her with a gentle and determined voice: “Don’t be afraid, still With me.” Su Yan was stunned with tears in her eyes for a long time, and finally, she reached out to Bai Xingfan.

- Description from Novelupdates

There are a total of seven sins, and a revelation is made to a young man named Alex that he is destined to become a demon lord, more especially a demon lord of sin called LUST.

It's not like he can change that and because he always knew something about himself was different—not in a physical sense, well, maybe a little—and not in a mental sense—but rather because he is thrown into a demonic war that compels him to accept his new reality.

He was only aware of a difference in himself. Relating to him and the ladies who are drawn to him... Well, it was more or less like he was a magnet in front of all the girls, and all the girls were drawn to him like a metal.