For the Young Villain's Happy Ending

I was reborn 14 years before the original novel began—as the empire’s strongest archmage.
All I remember is a single plea: “Protect them.” So I stayed low, planning not to interfere with the story’s happy ending.
But then I met the young Fourth Prince, the future tyrant shaped by tragedy. Gaunt and neglected, the child had never even tasted warm soup.
I couldn’t just watch.
“Your Highness, would you like to become my disciple?”
Twelve years later, the once-abused prince is a grown man—still my loyal student, and now hiding bold feelings for his master.