This girl would purposely dress ugly so that this guy would not like her but she is a beauty. She one day woke up in the past after getting killed, this time she decided to act strong to avoid getting killed. The main lead was this super rich 9th master that was the Boss and he was very possessive. Such as not letting her go to school, until she proved her loyalty etc. He was afraid she would cheat on him.
Once she woke up reborn from the past she realized he loves her. He also had a disease and bad insomnia but only in her presence did he sleep well. The lastest chapter I remember was when she helped prevent him from getting bad injuries by using information in the future. They were going to get attacked but she dresses up as a well known assassin group that had rose bracelet as proof.