This is a summary based on our understanding of the series.
Please also note that this summary contains spoilers.
Kang Chul is the main character of the webtoon made by Oh Yeon-jo’s father.
Yeon-joo was dragged to the webtoon (it turned out to be real) because the characters have become uncontrollable. She fell in love with Kang Chul, but conflicts like: uncontrollable villain & disappearing characters arose.
It turns out that Yoon Joo created Kang Chul when she was younger.
Yoon Joo ended up with Kang Chul in the real world.