With Amadeus deleted from history, Rintarou ends up in a slightly different present, in which Leskinen never succeeded in fully brainwashing Kagari. Moeka subdues Leskinen when he pulls a gun on Rintarou, and the two head up to the roof just as Mayuri is successfully stopping Kagari and Suzuha from killing each other, by badassedly positioning her head between their handguns. Mayuri and Suzu are able to board the time machine safely after receiving the blessing of a Rintarou who’d just arrived in that time.
All the times the time machine was wiped out by a missile from a helicopter gunship, it was only seconds away from disappearing into the spacetime either, so a few extra seconds is all Mayuri and Suzu needed to get away safely, and they do, in an extremely thrilling scene that pays off all of the failure and heartache of previous attempts.
Better still, Hououin Kyouma is able to lustily gloat to Leskinen, Stratfor, DURPA and the Russians for having foiled their plans to acquire the time machine. In the timeline where Mayuri and Daru await the return of Rintarou and Suzu, two time machines briefly appear on the rooftop at once, and Mayuri gets a call from…the other Mayuri, convincing her not to let Okarin give up when he returns in the depths of despair.
Mayuri and Suzu aren’t able to stay in that timeline long lest they cause a paradox, and with the time machine all but out of fuel, they soon lose the ability to choose their next destination. But both of them seem to take their descent into temporal oblivion quite well, all things considered.
Back on the rooftop, Suzu and a defeated, blood-stained Rintarou return, and he gives his little speech about everything being hopeless and deciding he’s going to give up. Then Mayuri remembers the words of the other Mayuri, recalls when Kyouma was “born” (when he hugged her to comfort her at the cemetery) slaps Rintarou, her Hikoboshi, and convinces him not to give up.
Soonafter Rintarou receives a video D-Mail from the Rintarou in the future, and we switch to his point of view, as we watch his grainy recording unfold where and when it occurred. After sending the message, Rintarou’s next operation, Operation Altair, consists of him “deceiving the world”, as well as himself, by travelling back to another point in spacetime in the first version of the time machine to be built by Daru & Co.
Deceiving himself and the world, it turns out, is the only way to reach the Stein’s Gate. He thanks his noble, trusty Lab Members, receives a hug from Maho, and sets off to locate and rescue Mayuri and Suzu, who were lost in time but can be found thanks to something called a “Kerr black hole tracer”, the nature and operation of which are not specified (which is probably for the best).
Suffice it to say, in his experimental but still brand-new and fully-gassed time machine, and with the Kerr thingy, Rintarou successfully locates Mayuri and Suzuha, who by their perspective had just arrived themselves in the year 18,000 B.C. in a dark and stormy wasteland.
They seem ready to accept their fate with grace, but the bright light of Mayuri’s Hikoboshi appears, and from that light, Okabe Rintarou—AKA Okarin, AKA Hououin Kyouma—emerges triumphant; perhaps his most badass moment yet.
And that, folks, is where Steins;Gate 0 ends things. We don’t get to see Steins Gate, or learn whether Rintarou is right that it does exist. All we know is that they’re in a good position to reach a world line in which both Mayuri and Kurisu can live.
It took a lot of gumption, guile, teamwork, sacrifice, trauma, math…and downright foolishness, but the gang is headed in the right direction. It’s a positive, hopeful ending; an ending full of promise and excitement for what may come next for all of these kind, brave fools—even if we may not get to see it.