OVA: Episode 23(β) Open the Missing Link

Released on December 3, 2015 titled as "Kyoukaimenjou no Missing Link-Divide by Zero"

This episode is an alternative to the 23th episode,

this is the prequel of Zero : It's in this worldline that the story will take place.

SPOILER

In its story, after killing Makise Kurisu, Okabe Rintarou gives up and accepts her funeral fate.

The main diffrence between this and the orignal 23rd episode is only that okabe never recive a D-mail to watch the news nor he was able to view the video.