Hitpoint

Ha On-Bit, a boy who suffered from heart problems after a car accident, has a dream where he is killed by an unidentified assailant. The relief of it being a dream only lasted for a moment, though, as On-Bit ran into that mysterious person exactly as it had happened in his dream. While he is running away, he comes to the realization that a deadly weapon that can destroy everything is inside his heart.

(Source: Naver, translated)

Note: Includes one extra chapter.