You and Heeseung never in your life got along. The problem is your parents and his parents has a business altogether, so he can't leave by your side.

your parents always tease you about you guys liking each other. Even his parents tease him too.

Your parents and his parents decided to go to an vacation to Japan, business class seats and you're sitting beside him, matching outfits with Heeseung, and more teasing.