MTL - Lord of the Mysteries - ~ The first summary and leave

In the back of the forest lives Allen, the antisocial wizard. He is feared by the people around him and called the “Demon Lord”.One day, while living out his life as a hermit, he finds a young girl named Charlotte who collapsed. Although innocent, she was accused of evil wrongdoings, had her engagement broken and was forced to flee her country.Upon hearing that, Allen recalled the bitter experience of being betrayed by a party he once believed to be his companions. Hearing the story of the 17 year old’s exploitation, Allen decides, “I’ll let her live in my mansion, and I’ll teach her all sorts of bad things…”

Doomsday was approaching…

"In her previous life, she is used by her first love to send her own company into the tiger's den. She becomes bankrupt, gets kicked out of the house by her father, and becomes the target of ridicule by the family. Worst of all, she believes her best friend's lies, thinking that everything was done by her ‘husband’. Under her best friend's ploys, she almost kills him and is ultimately sentenced to prison, where she dies of depression.

There was a Senior Brother and a Junior Sister. One of them was transmigrated to this world and had cheats while the other was the reincarnation of a Great Emperor.