The Advanced Player of the Tutorial Tower 

After being trapped for 12 years in a tower full of regenerating monsters, Hyeon-U Kim is more powerful than just about any human or monster on Earth. Now that he’s free, he’s determined to find out who was behind his imprisonment, even if that means he has to kill hordes of monsters — and inadvertently save the world — along the way. (Source: WEBTOON, edited) Note: Includes four extra chapters.