Argate Online

Takashi Izu, a.k.a. Rikio, is playing the VRMMO called "Argate Online" as he usually does when he notices that something is wrong. He is supposed to be maxed level, but he suddenly finds himself at level 1...?! He can't log out, and there is no pain absorber. It appears that he has entered a different world where the game has become a reality. But, experiencing a fantasy world in the flesh is even more exciting than when it was a game. With his extensive knowledge of the game system and his flexible ideas, he becomes a cheat samurai who can fight in battles, create his magic, and make a lot of money in his spare time! This is a unique samurai fantasy that you will enjoy from beginning to the very end!

(Source: Alpha Manga)