I'm trying to find the name of a manga about a guy transported into a strategy video game.
The manga starts with the main character winning the strategy game on the highest difficulty setting, then he gets a notice from the game creators and he is transported into the body of a weak and tyrannical noble who was killed before the game even starts.
This is I'm Now an Evil Lord In a World Where Only I Can Level Up.
Ryuuichi Hasegawa, the top player in a strategic medieval RPG, is granted a special "bonus" by the developer and reincarnated into the game world—not as the protagonist, but as the villainous lord Erhin Eintorian who dies in the prologue! This means Erhin's survival is a race against time, for his domain is set to be invaded by a hostile foreign power in just one day. ...
The opening goes as described - the protagonist is playing the strategy RPG game as the top player and suddenly gets a notification for an extra mode. He accepts, but nothing immediately happens.
He then goes to bed and wakes up in the world of the game as a minor character - there's no mention of his name, but he recognizes the name of the country as one that is promptly destroyed in the prologue.
This matches "I became tyrant of a defense game".
Protagonist finishes game at highest difficulty and is transported to game's world in tutorial level which is not meant to be survived. Later he meets "in-game assistant" that confesses that he is (kinda?) god of this world and he distributed gamified version of the world in many different worlds. He asks protagonist to reach a good ending.
