After Our Engagement, My Fiancé Developed Split Personalities [Crossover]

#This is the main story# So, I've been desk mates with the only son of a family friend since third grade. After spending time together in all sorts of ways, we moved up to middle school and stayed desk mates. Then we started dating. He said he wanted to make a marriage pact. I thought it was too soon, but I agreed anyway. Not long after we made our engagement official, he turned into a cold, ruthless, and obsessively competitive person. What could I do? Of course I had to stay by his side and help him untangle his heart, one step at a time. (Sigh...) "Rin, stay away from everyone but me. That's an order. Don't disobey me." I sighed, walked over slowly, and hugged him, resting my head on his shoulder and rubbing against it. "All right, all right. I know I'm yours alone." What else could I do? I had to humor him.