I'm predicting his only role is to come between jeongie and hangyul, which is sad we see this trope played a lot. He hasn't popped up in any chapters at all, only to be used to stir up trouble
I also don’t like it when this gets played but I sometimes do because it helps the characters realize their true feelings and sometimes speeds up the process
Nothing much really happened actually because all jangjae did was make hangyul make him get jealous. They end up getting together in chapter 38 which is not that long.
I'm predicting his only role is to come between jeongie and hangyul, which is sad we see this trope played a lot. He hasn't popped up in any chapters at all, only to be used to stir up trouble