They are both about a young boy who is wronged by the law. In both cases the boys have super-abilities (one is more ..fantastical than the other). Both stories also contain an older noona through whom the boy's goal of bringing the criminal to court is accomplished. This noona also serves as the love interest.
There are even parallel scenes.
In other words, they are pretty much the same, except for casting, music, and circumstantial differences. Soo Ha and Dae Gu would find they have waayyy tooo much in common, if they met.
Oh, but there is one notable difference: Hye Sun is bold and sassy throughout the show, Soo Soon only manages to be bold and sassy while she's still a teenager. That side of Soo Soon dies out once she becomes an adult.