There's 49 Left, Master!

There's 49 Left, Master! summary: When the powerless thirteenth prince became emperor, he gave his tutor, Yo Yohwa, poison. His reason being his death at the hands of his own master in countless previous lives. The poisoned Yo Yohwa then regresses to an earlier time together with the prince and is determined to get on his good side this time in order to escape. However, the prince already discovered the truth… “This is crazy. You killed me in the previous lives, and you neglected me in another. Now you’re acting all nice. Are you trying to get away?”