Heartless Darkness (Sekai/Chanbaek)

Sehun is a careless, innocent student who doesn't know the dark sides of life. Meanwhile, Kai is a cold-hearted guy looking for revenge after his beloved father got killed by Oh Seung Ho (Sehun's father). How will he seek his revenge? NOTE: I'm not a native English speaker; if you decide to read this story, count in...