Captain Necromancer, Opening up the Continent of the Dead

[Undead + Alien World + Ten Thousand Races] Captain Os from another world summoned Van Os, whose name was similar to his own, and his soul was replaced by him. And Van Os wakes up to find that the crew are all dead souls. He also possessed the captain and boarded a ghost ship. I had no choice but to learn the undead magic left by Captain Os. In order to understand the reason why I came to this world, I came to the mainland and started to search for the reason why I came here.