Chonchu (also known as Chunchu) is a manhwa (Korean manga) by Kim Syung Jae and Kim Byung Jin. In this violent fantasy, the title character is a young man known as the Son of The Demon because of the Demon Stone embedded in his chest. The stone gives him strength and makes him virtually immortal. While his twin brother is the king of an empire, Chonchu is reviled and many people try to kill him in order to gain the huge bounty.
If the style of artwork looks a little familiar, it may be because artist Kim Byung Jin does the art for a manga called Jackals (which will probably get its own post sometime in the future).
Chonchu was licensed by Dark Horse Comics for release in America but after putting out just three volumes, it looks as though it has been abandoned.
Image Archive (.zip)