Now lets start with the events that are probably going to happen in episode 23 & 24: World War III, again Kurisu is the cause of this
because she is dead. Kurisu's death is essentially a Schrodinger's Paradox, this type of Paradox has to happen in order to stabilize the Timelines Attractor Field and Butterfly effect.
The Attractor Field is the Timelines ID, it is what makes a specific Timeline unique from all the others, the Attractor Field being peoples encounters and whatnot, failure to preserve an Attractor Field usually leads to a Butterfly effect so great it gives you a different Timeline entirely.
Now who killed Kurisu, Okarin did. Now as to why i called this a Schrodinger's Paradox:
A. A canon spoiler says he killed her accidentally, Suzuha meant for this to happen otherwise he would have fallen into a Paradox:
Now lets expand on Suzuha's warning, when they went back in time to prevent Kurisu's death & WWIII
Suzuha warned Okabe not to run into his past self otherwise the chance of a Paradox was high.She also threw away his phone as it could cause problems later
possibility allowing SERN to trace them again if she didn't.1. It could be because SERN!Okarin
The Okarin who eluded SERN in the anime when he went to save Kurisu
after saving Mayuri from the SERN fiasco, the struggle against DR Narakabechi took too long causing him to run into Pawn!Okarin.
2. A disturbing canon spoiler suggests that she needed to die in order for Pawn!Okarin to time travel in the first place, if Pawn!Okarin saw her alive then SERN!Okarin's path would have been nullified.
And now for the Schrodinger Paradox, after SERN!Okarin fails to save Kurisu, Suzuha says she needed to die in order for him to see the D-Movie from ??!Okarin in 2032, SERN!Okarin asks why he didn't come to tell him himself, Suzuha explains that is because ??!Okarin died soon after.
Some events happen with the motherfucking Metal Uupa soon after, Suzuha tells SERN!Okarin to turn on the tv which broadcasts a plane crash with DR Narabachi still alive holding Kurisu's envelope involving time travel that in which he stole from her in order to proclaim as his own, the letter survived because of the Metal Uupa.
Suzuha now provides him the D-movie.
He watches the D-Movie, 2032!Okarin provides a way to deceive the Attractor Field so at the very least it is non fatal
depending on who / how many people are viewing the event at the time, he tells SERN!Okarin to go and make it look as if Kurisu "died"
-Now it is a mystery as to whether Kurisu's original "death" was caused by Suzuha / Paradox!Okarin or AD!Mayushi- Revitalized after watching the D-Movie he now becomes SERN2!Okarin then goes back to save Kurisu.
The world diverges and it shows SERN2!Okarin wandering around Akibaraha, he runs into Kurisu who thanks him for saving her, he mocks her calling her Christina as usual, "I am nether Christina nor an
assistant!" this shocks both of them as he never called her assistant in this timeline, he then deduces that everyone has reading steiner, but because of the 4th wall effect we thought Okarin was the only one who had it.
Ahh at last we can now finally explain this:
http://www.goodanime.net/steins-gate-episode-12The first few minutes of ep 12.. probably after saving Kurisu the one that dies is
himself, which kick starts Mayushi's 70,000,000 years time travel crusade, adds a new layer of fridge horror doesn't it?
And this, skip to 16:22:
http://www.gogoanime.com/steins-gate-episode-6/2This is Okarin being pulled into the Hadron Collider and getting jellified in the process.
An important thing to note here is that Kurisu said
Space and Time had swapped places, followed by
"You mustn't look back, Eternity isn't infinite, even if Time stretches towards Eternity, an end still exists." Okarin seems to be conscious
of the entire Colliding process when he says
"When will it be 1 second later?" this seems to be related to the Mayushi' 70,000,000 million years arc.