It's The Apocalypse and Turns Out I'm A Vampire Vamp Apocalypse

Also known as Vamp Apocalypse
Hey there! My first time writing this kind of novel and I don't really know how to write a synopsis for it, so please support it!

Kwon Sung-ho is a 17 year old teen who is heralded as the Dark King in his high school. One day, on the way to school he meets a girl who is about to commit suicide. He convinces her against it, but while she ran away she dropped a pocket watch which he picked up.
Afterwards he goes to school, where he gets detention. While in detention, he falls asleep and when he wakes up, he sees a screen in front of him telling him that its the apocalypse.
Later on, he is killed by a swarm of monsters, but then he wakes up with a screen telling him
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