hm? I though heesung and dojun can't have kids that's why they got a dog?

she's their adoptive kid, it's stated in the main story

If you just skimmed through the sides of the main story, I understand why you didn't catch a glimpse of her, her introduction was literally just a panel at the end of that one chapter where she was eating outdoors with heesung and dojun, and then that's it, no other panels about her after, next time we see her is in this work.

OHH I SEEE
yeah I must have missed that, thanks for explaining!