This webtoon is adorable, a veritable roller coaster of crying and giggling (more crying) as you empathize with the emotions of the characters and how they deal with prejudice, family tension, bullying and other issues or how they grow to value each other, their loved ones around them and slowly grow up.
Note that despite the intended gravity of the subject of disabilities, Lee Jun actually focuses relatively little on the intricacies of these, which might chagrin some readers who were looking for a more realistic portrayal of life with disabilities. As Wotonito mentioned, there might be some superficiality on certain emotions as well. I'm still a bit confused as to how exactly Da-jeong is supposed to behave, considering she's a 19 year old but looks like a 9 year old. She often acts like a child, despite her experience and perhaps her supposed rejection of being a child. Nevertheless, I often find myself thinking that that's not innaccurate, considering that most of us, as we age, don't necessarily feel all that much more matured, and considering that hormone levels and other factors of a child's body would play an important part in character.
And, whatever the extent of the realism or incomplete depiction of disabilities or the full range of emotions, where Lee Jun's crafstmanship really shines is in bringing together the different elements of our empathy, the characters' moods and very natural events to propel the human drama, making the series so touching and unique.