What is "That Time I Got Reincarnated the TTJRPG?"

After watching 5 or 6 isekai themed anime shows in my time, I wondered, what if a TTRPG was designed to insert players into the roles of people who then by portal, truck accident, or magical artifact are sucked into another world?

Beyond just playing characters, you are playing people who are playing other characters. You might be Devin in real life, playing Jamie in the game, who reincarnates and is called Bo-Sivar the Fire Sorcerer. So players are called Meta-Players

The Game Master, the common generic term, has been replaced by Rangler, an etymologically similar word to Wrangler, with some variations, but also, the letters in the order are RNG, which is a pun on Random Number Generator, the system behind most video game RPGs. So the RNG determines when the players hit a wall, or require a skill contest to continue.

tTIGR utilizes a system where only the players roll dice. It is a percentile roll-under with a twist, but in this, the RNG never touches dice unless they are rolling loot tables. Otherwise it is an entirely player-centered game, for a reason...

The premise of the game is that the world moves because the players in it are engaging with it, so the focus should be everything revolves around their decisions and actions. 

NPCs engage in response,

Monsters arrive to cause tension,

Quests move the world forward,

The plot centers on the Party.

Now, that is not to say that the players have to be present in order for the world to move forward, but their exploration expands the world. 

The game does not come with a pre-set universe, what happens is the players begin in a single location, and collaboratively can grow the world by exploring.