This is of course the world line that Okabe spent most of Steins;Gate in and also the one where Mayuri is dead.
In an expanded version of one of the more prominent scenes from the game, the end of episode 7 and episode 8 of Steins;Gate 0 sends Okabe back to the Alpha world line.
Even with Kurisu’s help here in the Alpha world line, she can’t make that all go away.