What really happened two year ago?

When school boy Park Seonghwa goes missing the public are shock.
They are even more shocked to find that his best friend Kim Hongjoong is the main suspect.
But when no evidence is found and Kim Hongjoong gets released due to the lack of evidence, the public don't know how to react.
Eventually the case goes cold.
And no dead body is found?

Two years later one student becomes to interested in the bizarre circumstances of this case and begins to look into it.
Along the way he finds it very interesting in how the missing persons case of Park Seonghwa seems very familiar to that of the case of Jung Wooyoung who went missing exactly two years before park Seonghwa.

And suddenly it seems that there is more to both of these missing person cases. Who did it?,
And what really happen to the school boys?
Where did Park Seonghwa and Jung Wooyoung go?
And why is there no dead bodies?