Wait why did he enter the palace 100 years ago? I forgot cuz my memory is really bad

Your memory didn't fail you. How they met and how he entered the palace were only explained in chapter 26-27.

He originally lived 100 years ago, but killed himself bc he couldn't handel the seme (late emperor) but bc of how many people died because of him (how many the emperor killed bc of him) he was reborn 100 years later

Thanks guys :)