You were a successful general in war. In the end, your 2nd in command, Scaramouche, betrays you, slicing off your neck. You reincarnate as the crown prince/princess of the enemy nation.

Scaramouche is assigned to protect you. He recognizes you, and when you're alone, he sneaks up behind you, and hugs you from behind..

"I miss you… being apart from you was an aching pain in my heart… I missed you, my commander.”

causing you to detest him more than you already do.