I Became the Tyrant of a Defence Game 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.nl fastest updating comic site. The Summary is

Tower Defense & Dungeon Attack RPG I saw the ending to the game no one was able to clear. But, when I came to my senses, I was inside of the game. In fact, I was in the tutorial stage, a place where strategy was impossible. “I’ll clear this bullshit game no matter what……!”