Spoilers All:

In episode 1, Okabe sends the 1st D-mail, changing the world to the Alpha world line where Kurisu lives instead of dying. In episode 22, They reverse this by having Daru hack into SERN and remove the information from their database. This means that SERN knowing about D-mail (or about Kurisu's death) somehow prevents Kurisu's death in the first place.

What is the chain of events that keeps Kurisu alive in the Alpha world line?

(Alpha is the world line with the SERN dystopia (Ep 2-22), while Beta is the one with World War 3 (Ep 1, 23, 24). )

  • 2
    I marked this spoilers all, but upon rereading, It's probably nothing but gibberish to someone who hasn't seen the show. Commented Apr 2, 2015 at 13:45
  • I'm trying to find a source, but it was explained to me once that Kurisu and Dr. Nakabachi were both invited to lecture in the Alpha line. Something about the Beta line (I can't remember what) caused Nakabuchi to no longer be at the lecture Commented Apr 2, 2015 at 13:46
  • 1
    Also, half of that show's plot is gibberish even if you have seen it Commented Apr 2, 2015 at 13:46
  • The thing that throws me is that whatever is different about Beta, it must be by deleting the record of the D-Mail from SERN's servers. There's probably off-screen time travel involved, since this is backwards causality. Commented Apr 2, 2015 at 13:52

3 Answers 3


How is Kurisu alive in the Alpha line?

This is a complicated question, but it basically comes down to Suzuha.

By sending the first D-mail, Okabe accidentally tips off CERN about time travel. Armed with that information, SERN develops their own time machine and eventually takes over the world (I'll get back to this point later).

Operating on instructions from her father, Suzuha takes a makeshift (and, because of SERN's monopoly on time travel, low-quality) time machine back to 2010 in an effort to stop SERN's rise to power. Because her co-ordinates are slightly off, she materializes in the roof of the Radio Building, rather than on it. Because of this, Dr. Nakabachi's conference is cancelled, he and Kurisu never meet there, and she doesn't get stabbed.

How did CERN develop time travel?

One of the steins;gate mangas, Shijou Saikyou no Slight Fever Chapter 3 "Muffled Phone", reveals that Kurisu went back to the Radio Building a few days after joining the Future Gadget Lab, and leaves her time travel thesis (the one she wanted to co-publish with Dr. Nakabachi in the Beta Line) there, where it is stolen by Moeka:

Kurisu leaves her thesis at the Radio Building

Moeka steals the thesis

Presumably, Okabe's D-mail puts SERN on Kurisu's trail, and CERN uses this thesis to develop their time machine.

It's also strongly implied (if not stated outright) that the members of the Future Gadget Lab are taken into custody by SERN after they complete the Time Leap machine; Suzuha's intervention gives Okabe an opportunity to use the Time Leap machine and change his fate, but without her then SERN would have had more than enough resources to create their Time Machine, take over the world, and create the Bad Future that prompts Suzuha to go back and disrupt everything.

I hate temporal mechanics.

Okay, so what does deleting that D-mail do?

This is an odd case, and not explained very well.

Not having this D-mail in their database somehow prevents SERN from successfully developing a time machine1.

If the "jellyman" files are any indication, SERN's own time travel research was a stunning failure, and they would almost certainly have abandoned it. Kurisu's thesis is likely very theoretical, and wouldn't have given them the crucial insight that allows the Future Gadget Lab to develop the Phonewave and Time Leap: the notion of sending back data rather than matter.

It seems as though SERN really needs to get their hands on those devices, as well as the three who invented them (Okabe, Kurisu, and Daru) in order to successfully develop time travel. Without it, we end up in a different future where Suzuha:

  1. Still needs to travel back to 2010
  2. Has a better time machine (because SERN doesn't have a monopoly on it anymore) and is able to land on the Radio Building without crashing

With Suzuha not crashing, Kurisu is able to give Nakabachi her time travel thesis, which ends up getting her killed and getting us back onto the Beta World Line.

1 It's the how of this that I can't rationalize. I have a couple of theories, but none of them really pan out:

  • CERN hadn't yet looked at the text when Daru deletes it. Within the show itself this is plausible; Moeka appears to stumble onto the Future Gadget Lab entirely by accident, and then sticks around once she realizes what they're doing. However, the manga referenced above makes this a hard theory to swallow; it really seems like Moeka was specifically targeting Kurisu, which she'd have no reason to be doing unless ordered to by CERN. This theory is supported by an episode Q&A on ibm5100.net. However, this appears to be a fansite, and is about as canon as anything I've speculated on.

    On reflection, it occurred to me that it's entirely plausible for Moeka to have been assigned to tail Kurisu and/or Dr. Nakabachi independently of the D-Mail, especially if CERN somehow became aware of Kurisu's time travel research. As far as I know there's no evidence for this, but it does somewhat redeem the theory.

  • CERN follows up on the lead, but ultimately decides that it's a dead end. Obviously the Future Gadget Lab isn't going to be pursuing any more time travel experiments after Okabe went through so much trouble to undo all those D-mails, so it's possible CERN eventually told Moeka to stand down after nothing came of this development. However, if that's the case then why bother deleting the D-mail? Okabe could just swear off time travel research, and we'd end up with the same result.

Unfortunately I can't come up with a satisfying explanation. "Because story" is, I suppose, the only thing left that makes sense.

  • In the Alpha world line, the Rounders attack when they threaten to go public with the time travel. So someone (at SERN?) already knows what they're doing. They delete the D-Mail after that date (but in a modified world line.) But that's enough to throw SERN off their track. Maybe FB alerted SERN in the world line where the Rounders attacked? Commented Apr 2, 2015 at 15:00
  • @SeanMcMillan Moeka knows, which means FB (and likely CERN as well) knows. This was never entirely clear to me either, but apparently deleting the D-mail from CERN's servers and preventing the D-mail from ever being sent are one and the same. By deleting it, it was never sent in the first place Commented Apr 2, 2015 at 15:06
  • Ugh. The Rounders attack on 8/13 (The first time we see them attack, anyway.) The D-mail is deleted from the SERN database on 8/17. So something happens after 8/17 that depends on the D-Mail, which leads to SERN dystopia. The Rounders attack must be independent of the D-Mail. So SERN is up to no good. And the jellyman files show that SERN is working on time travel already. Commented Apr 2, 2015 at 15:12
  • My best guess is that the Rounders attack was organized locally, based on Moeka's information, and when that was undone, so was the attack. And that later (days - years,) someone at SERN notices the D-Mail in their database and it alerts them to Kurisu's importance. She builds time travel for SERN, leading to the alpha world line dystopia. Suzuha calls Kurisu the mother of the time machine, and says she works for SERN, IIRC, so this works out, kind of. Commented Apr 2, 2015 at 15:15
  • @SeanMcMillan I've done some more thinking, and made an edit. I don't think it's unreasonable to suggest that CERN abandoned their time travel research; the jellyman trials looked pretty disastrous, and because they didn't know about the Phonewave (which was an accident, remember), it may never have occurred to them to try sending data rather than people Commented Apr 2, 2015 at 15:23

My theory is that SERN has developed DMail and that deleting Okibes first DMail from their files would prevent SERN from seeing it in the future, putting the pieces together and then putting SERN agents in the past into action via their own DMail.

It stands to reason that if SERN is doing human testing then they are exploring every option that they have, and we also know that they have already invented DMail, but are misusing it in trying to send humans rather than data back in time.

Perhaps they are aware of this (their last human testing was years ago), and thats why they are interested in digitizing consciousness and therefore in Kurisu.


Y'all theorizing while it's literally explained in the 2nd episode that the satellite collapsing into the building got the conference cancelled and that is why Makise never attended the meeting. That's why she ended up being alive after the change.

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    Hi, welcome to SF&F. Since the question is about how the existence of the D-Mail somehow preserves Kurisu's life, is this sequence of events affected by the D-Mail?
    – DavidW
    Commented Jan 10, 2022 at 16:25
  • 1
    That's true, but it's not quite going back far enough. What caused the satellite crash? How is it linked to the D-Mail Okabe sent? Can you edit your answer to explain that?
    – F1Krazy
    Commented Jan 10, 2022 at 16:47
  • How does hacking SERN make the satellite (Time Machine) not hit the building? Commented Jan 11, 2022 at 18:07

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