And so Natsuhiko tells her that he’s after a man. He was once a scientist, but is more of a weapon dealer now and is selling them to many countries and hence spreading war. His goal is probably to make 2056 happen again. When Mikoto brings up Sorata, Natsuhiko guesses that he probably came from the 3rd world – the world has been reset numerous times and currently this is the 4th world. And it’s the power users who make that possible. He decides to leave this talk for another time. It’s no use just stopping one conflict, and better to kill the source, which is the weapon dealer. To deal with him, Natsuhiko has been researching on weapons to counter attack, but he could do with her ability too. He believes that without that man, a time can come when science wouldn’t be abused. Mikoto feels that it’s a good thing to stop war, but doesn’t understand why he’s after their lives. Natsuhiko is willing to not kill them for now, if she cooperates, as he knows that they won’t reach their destination till much later. As Mikoto opens up to him about her suspicions from before, he commends her on having thought that much as a frequency running in the ship which prevents them from thinking about information which can’t be disclosed. He confirms that they’re being deceived, and asks her to cooperate if she wants to know the truth. Mikoto agrees in the end, though she gets shaken when she realises that there are other men aboard (Setsu). Thinking that everyone is a sadist, she chases them out and even casts a barrier 24/7.After that, Mikoto cooperates with Natsuhiko and is no longer handcuffed, or threatened since that day. She gets freaked out one day when Natsuhiko arranges for a large robot to attend to her and misunderstands his intentions. So he then arranges for a white Hiyoko, modelled after those on Norn, to attend to her. Mikoto slowly opens up to it's kindness, not knowing that Natsuhiko is the one responsible for writing its lines on the green board its holding. One night, Natsuhiko brings her out to see the stars. Seeing the full moon, Mikoto remarks on how it’ll be fun to travel to it. Natsuhiko replies that it’s possible one day – they will discover new things with research and he feels touched at that. He thinks that it's probably what motivates scientists and that’s how they fulfill dreams. Mikoto starts to think that Natsuhiko isn't all that bad, and thanks him for the Hiyoko. He tells her not to push herself, though the only thing he can’t do is let her return. After that, they started spending more time star-gazing and he would teach her what he knows about stars. On a rest day, Mikoto reads a book on stars Natsuhiko gives her and learns about Arcturus and Spica which are known as the husband and wife stars which would slowly get closer to each other as time passes. Wanting to share this with Natsuhiko, Mikoto goes to find him but overhears his conversation with Setsu . It appears that Setsu is going to infiltrate Shirō ’s side to find out which countries he’s involved with, where is his HQ, and how long more can Shirou last. Natsuhiko wants Setsu to return before they kill the power users. Mikoto dashes back to her room, not knowing why she feels betrayed even though she knows fully well the circumstances. She pours out her feelings to the white Hiyoko, wondering why he treated her so kindly if he was going to kill them.
Natsuhiko suddenly barges in and hugs Mikoto. Mikoto starts questioning him, asking for the truth and adding that none of them ever wished for their own power. She promises to do anything as long as he doesn’t kill them, and Natsuhiko hugs her tighter. Slowly, he tells her that their powers are meant to Reset the world. In 2060, WWV was impending and all other culture was dying out as countries kept buying weapons as a means of defence. At this rate, the world is bound to end as some areas are already not fit for living. In 2085, it was decided that they’ll Reset the world. But humans kept going in the same cycle and this is the 4th world. Aion will use her returned powers to Reset the world. Natsuhiko tells Mikoto to take as much time as she needs to wrap her head around this. He adds that he’s opposed to Reset, and that’s why he’s after their lives. Moreover it’ll be dangerous if Shirou abuses their powers. After Natsuhiko leaves her alone, she suddenly hears Heishi’s voice calling out to her, alongside Nanami and Koharu’s. While she can’t repond to them, she feels comforted. Just then, the ship is under attack but Mikoto can’t set up a forcefield in time. In the end, Natsuhiko protects her from an incoming attack as the ship crashes. He then carries her all the way to a nearby village for help before passing out. Mikoto wakes up 3 days later with no harm, but learns that Natsuhiko is in a more severe condition. When left alone, Mikoto sees that this is her chance to kill Natsuhiko with his gun but can’t bring herself to do it. She wonders for what purpose she lived – all along she thought it was to protect people, but now she’s told that it’s for Reset. Moreover, Natsuhiko saved her despite them being enemies, and her failing to use her forcefield during that critical moment. She couldn’t do so as she was conflicted as to whether to die just like this, or to block the attack.Soon, he wakes up but fails to remember anything except Mikoto’s name. They stay here while Natsuhiko recuperates though he shows no signs of recalling his memory. One night, Natsuhiko has the urge to go outside to see the stars. Mikoto accompanies him and tells him as much as she can about the stars, including Arcturus and Spica. When they return, Natsuhiko asks what he is to her. When Mikoto is unable to answer, he asks the opposite instead. In reply, Mikoto says that she’s a tool to him as he threatened her with her friends’ lives. Natsuhiko wonders why she’s taking care of such a cruel man then, she could’ve just run away. In return, Mikoto asks why he protected her then. Natsuhiko is sure that he wouldn’t have done that if she were a mere tool. Whether he gains back his memory or not, he knows himself best and sees her as important. He promises not to hurt her again and to believe in his feelings as he wants to protect her. And as Mikoto returns his feelings, he takes her to bed. It feels as though the gap between them has been shortened, just like Arcturus and Spica. The next morning, Natsuhiko cooks breakfast and Mikoto observes that the porridge is pretty much boiling – which makes her recall their first conversation in which she complained about the cold porridge. But she wonders why Natsuhiko remembers it. All of a sudden, Ron comes in and Mikoto tells him that Natsuhiko has lost his memories. Seeing that this is the case, Ron remarks that their agreement is void now and draws out his guns. Natsuhiko soon responds and Ron notes that he regained his memory after all.
While Mikoto sees that their temporary peaceful life is over, Natsuhiko reassures her that nothing will change – his feelings for her remain the same and he promises not to kill the Norn members. Later, Natsuhiko gets updated on the situation from Setsu. Apparently Shiro appeared in Norn and pointed Ron out as the betrayer, and so Setsu had to step out and save Ron. However, everyone has been deceived by Shiro especially since Kakeru went to Shiro’s side. Ron did try to remove Kakeru’s earring to stop the brainwash but he failed. Natsuhiko explains to Mikoto that Kakeru isn’t Shiro’s blood-related son and probably took him in because of his powers. Natsuhiko orders Setsu to check up on their whereabouts, while he works on a weapon to counter attack Shiro. Later, Natsuhiko goes to find Mikoto. When she denies that she’s worried about anything, he draws her into his arms instead. Though her lack of honesty does annoy him, he’s also started to take a liking to it. He opens up to her as he says that he’s always hated them since they’re the ones responsible for Reset. Once they do so, everyone loses their memories and all the research is reduced to nothing. While he knew that it was the last resort to stopping the war, he couldn’t bring himself to forgive them. He also hated Shiro for using science for his own selfish gains. He points out to Mikoto that unlike her, there are people who abuse their power for monetary gains. However, just as she previously said it’s not like they wanted these powers in the first place and they’re human just like the rest of them. Mikoto observes that just as how she was driven by the sole thought to protect everyone, he was driven by his hatred of them for a long time and that has worn him down.That night, Natsuhiko brings Mikoto out to see a meteor shower which occurs once every 1000 years. He tells her that humans once travelled to outer space in the past. He also explains that Aion, known as the World to them, is the one who chooses the power users and have them decide on whether to Reset the world or not. He’s the descendant of the scientist who created Aion, and his people live on a small island to see to Aion and see that Reset is done properly. Natsuhiko plans to go meet Aion. While Reset may be the best solution to stopping Shiro, he wants to see the future of mankind where science is used for better reasons. Days later, they arrive at the island and Masamune is there waiting for them. Inside, Mikoto is reunited with the rest though they don’t adopt a welcoming attitude to Natsuhiko. Also, Kakeru is not with them, and Sorata is currently talking to Aion. Masamune explains that when Mikoto went missing, he tried to contact Aion but he couldn’t so he went to meet her on his own. During that time, Shiro came onto Norn and outed Ron as a betrayer. He asked them to come with him and with Kakeru’s lead, Koharu, Senri and Sakuya followed. The rest remained behind, and waited for Masamune’s return. While Akito thought that it was weird for Kakeru to accept his father (who should’ve long been dead) so casually, Koharu also knew Shiro from before and recalled him saying that he had no kids. They followed Kakeru as they were worried, and sensed something wrong when they were told to fight. However, Shiro died and they managed to escape amidst the chaos with the help of Masamune – but without Kakeru as he’s no longer the same as before. When Natsuhiko questions why Shiro died so suddenly, Masamune hints that he’s the same as Aion.
Ron then bids farewell to Natsuhiko, as in the end, he couldn’t kill Shiro or any of the Norn members so his work is done. He drags Setsu along though to send him back. Inside, they meet Aion who explains that even if Shiro has died the weapons he’s distributed everywhere has already sparked off conflict. Natsuhiko is prepared to deal with that but Aion wonders why he won’t choose Reset as an alternate solution. Natsuhiko sees it as a mistake, and thinks that they should improve on Aion so that no one can oppose her and she can govern over all the countries. But Aion points out that the idea of letting an emotionless robot rule them was rejected, and it was a compromise in which she became Aion – she was built with a heart inside of her in the first place. It’s too much of a burden for a robot to guide mankind. Also, if Natsuhiko destroys the weapons Shiro distributed with his own it’s still a war so the best solution is still Reset. She persuades Natsuhiko to abandon his weapons. Humans are afraid to lose that power so instead they keep investing in it and it eventually leads to conflict. While Natsuhiko speaks for the good of humanity, he himself doesn’t want to abandon his own weapon.
Tragic Love End: Natsuhiko isn’t persuaded, and sticks to his initial goal of ending the Reset cycle. He doesn’t listen to Mikoto’s words, and calls for Setsu and Ron to return. When Mikoto begs for him to bring her along, Natsuhiko refuses to. Sakuya holds Mikoto back while Natsuhiko leaves, telling her that Natsuhiko has already chosen to rid of all weapons over her. Mikoto knows that she was unable to change Natsuhiko, but still she can’t deny her feelings for him. After that, Natsuhiko never returned and probably never told her to wait for him knowing that he can’t. Some time later, it was known that Natsuhiko was killed and Mikoto is unable to accept that reality and a future without him. In the end, Nanami erases her memories of Natsuhiko and Sakuya plans to take her back to their hometown. While war is still ongoing, Sakuya thinks that it’s better to act earlier and will protect her even at the risk of his own life. Meanwhile, in her sleep Mikoto dreams of herself sleeping in a sea of stars besides an unknown person (Natsuhiko).Happy End: Natsuhiko gives up his weapons and after that each of them start heading on their own separate ways. They chose not to do Reset, and returned their powers to Aion – except Itsuki and Heishi who fled the island. Masamune is still trying to catch them. Though later, Mikoto learns that Natsuhiko helped Itsuki and Heishi escape as they want to save Kakeru. Natsuhiko and Mikoto remain behind to research on outer space, as well as to compile all the different progresses mankind has made since the last Reset. And today, Koharu, Senri, Nanami, Akito and Sakuya are returning to Japan. Mikoto writes a letter to pretty much every family member (even Sakuya’s) and passes the bundle to Sakuya. Sakuya tells her to be happy and to improve her drawing skills, and tells her not to send them off knowing that she’ll end up crying. He adds that he once thought that it would be alright to die protecting his important person – but now he feels happy to have a future. Afterwards, Natsuhiko spots Mikoto tearing up though she still puts up a strong front. He overheard their conversation, and brings out the drawing Mikoto drew of him. Apparently Ron sent it to him in exchange for not being able to kill Shiro. Natsuhiko starts teasing her as he brings her hand to his face, and asks if his face is that twisted.
Natsuhiko remarks that the him before was so hung up on his duty, that he lost sight of what’s really important. Even though the world hasn’t been changed, he feels as though he is filled with happiness thanks to her. In response, Mikoto brings up their research and she’d like to go to outer space herself one day – but if they can’t she’s alright with her children fulfilling that dream too. The future way ahead of them appears bright to her as she’s with Natsuhiko. Just then, Mikoto sees the ship everyone is supposed to leave on flying past. Natsuhiko tells her that while they can’t travel to outer space now, they can go to see her friends anytime. After all, he fell in love with her crying face as he found it beautiful.