Alternate 23rd episode of Steins;Gate, which leads into the story of Steins;Gate 0. It will be included with the Steins;Gate Complete Blu-ray Box.
The main difference between this episode and the original episode 23 is that Okabe does not open the Movie Mail from his future self, due to Mayuri begging Suzuha to stop relying on Okabe to prevent World War Three. By not opening the Movie Mail Okabe does not find out about Operation Skuld and is unsuccessful in averting both Kurisu’s death and World War Three, thereby leading into the story of Steins;Gate 0
(Source: Steins;Gate Fandom, edited)