Starting as the Black Dragon BOSS is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

The game has turned into reality, the era of the changing classes came! Su Yang changed his class and became a simple warrior. But unexpectedly, he discovered that he had turned into the Level 99 Black Dragon Boss as well? The first time he tried to connect with the BOSS, he encountered a level A guild standing in front of him? Facing those class changers who were armed to the teeth, Su Yang casually spewed a mouthful of black fire- [You have wiped out the “Spirit Hunt” guild] [Exp gained +990,000, level 1-20 (exp overflow, please change classes as soon as possible] [Obtained loot: Diamond Rank: Great Sword – Storm’s Call, class change scroll…] Slowly, the Black Dragon BOSS changed into a level 999 Abyss Lord. Su Yang realized he seemed to be invincible?