It seems like our ML has relived his life many times and loves the FL dearly. He wants to protect her and allow her to do all that she wants to do. He doesn't push her into a relationship but allows her to slowly develop feelings for him. They have misunderstandings but seem resolved in a few chapters at most.

She has finally accepted dating the ML and their first date was to a secret library only for the imperials where she spent all day reading to the point that they missed dinner but he just allowed her to do as she liked.

His tyranny is to protect her - he kills his family because they were partly the reason for her death in the past. He falls in love with her in his first life, she became his teacher and she was the first teacher he ever had who actually taught him. He ended up idolizing her and wanting her to be happy but she ended up dying partially to protect him. He spends the rest of all of his lives trying to keep her safe but she always dies.

In his first life ML was the neglected 3rd Prince born to a maid/lady in waiting(?). He was horribly neglected growing up and the Empress was constantly trying to poison him and torment him. She assigned him abusive tutors that would whip him.
He has magic ability's a 'golden mark' of a true emperor that allows him to have special abilities and powers, but he hides this his whole life to avoid getting swept up in succession battles.
He met the FL when she was assigned as his tutor. He was grateful to her because she was willing to patiently teach him things and he wanted to make her proud since she was one of the few people who was kind to him. After a while FL is fired as his tutor and leaves the palace, but he keeps studying and wants to meet her again some day.
Fast forward to the future, years later - multiple disasters have struck the Empire and there is a rebellion starting. The FL shows up to the MLs palace to help the Imperial family broker a deal with the rebels. She miraculously succeeds but then the trash Imperial family breaks the deal and only escalates the rebellion. FL is sent to try and renegotiate and the ML reluctantly lets her go because she convinces him not to come with her. The FL is sad that she lacks the power to truly fix things but is desperate to try. By this point she is deeply precious to him and is the only good person he has left in his life. She dies, horribly and violently, and the trash Emperor and Empress call her a traitor for trying to negotiate with the rebels.
The ML snaps and murders the corrupt Imperial Family before killing himself by stabbing himself in the heart. He wakes up in his child body surprised to be alive.
It's explained in later chapters that the ML has turned back time dozens of times and FL died in every timeline no matter what he did. But they were never romantically involved until this timeline. The ML only wanted her to be able to succeed and live happily since in every timeline the FL's talent was written off despite the fact she was more than capable of saving the Empire from misfortune. He even watched as she married other people, but she died horribly every time, and he always turned time back.