I'll give you guys a hint on that pokémon rival guess thing. It's not anyone from Alola (which rules out...two people right?). That's all I can tell ya for now. On with the story!
____________________________________

       (Y/n) quickly headed down to her pokémon lab to gather some essential data on the Necrozma from Alola's original crisis. It had been about a week since she'd last chatted with Necrozma through telepathy. Yes, (y/n) had entire telepathic conversations with the psychic pokémon. She'd even given Necrozma the shortened nickname, Neroza.

       (Y/n) was the only human that Neroza willingly communicated with and was considered by Neroza to be a good friend. (Y/n) was sure to treat Neroza with kindness especially after Neroza had apologized for what had happened so long ago. In fact, Neroza had often helped (y/n) with her ultra wormhole research.

      (Y/n) went into her lab and searched through her computer files for a folder containing all of the video recordings that she took of her, Rei, Neroza, and Lunala whenever they were researching together.

        Lunala wasn't always there but Rei certainly was and thinking about her precious pokémon made (y/n) wonder if her was okay. She'd had to leave him with the others back when Moon began her attack.

       (Y/n) finally found the file that she was looking for and loaded it onto one of her flashdrives. It was a file folder containing the reports from every one of the videos she'd taken. They would be useful so (y/n) copied the file onto one of her flashdrives.

        She quickly grabbed her laptop and put the flashdrive along with a pen into her pocket. She then headed to where Neroza was waiting for her on the separate part of Aether.

       The small island was connected to Aether by a long pathway with railings to make sure no one fell into the sea while trying to get there. (Y/n) was about to head out of the main entrance but stopped when she noticed all of the people that were unconscious on the floor. Not even the few pokémon there were spared.

        "Crap, she's already here," (y/n) muttered to herself as she quickly leaped over the reception counter and hid behind it.

       She wondered how she was able to remain unaffected by the psychic pulse of energy that no doubt went through the facility. She wasn't in contact with Lunala who was still outside and not making a sound.

        "(Y/n)...I know you're in here somewhere. Stop hiding, (y/n). I won't hurt you," Moon's voice said throughout the room. (Y/n) couldn't tell where it was coming from and that really bothered her.

        "Your friend Sun is here to say hello. Why don't you come out and greet him?" Moon cooed. Her taunting was rather tempting but also highly annoying.

        "Don't do it (y/n)! Don't listen to her! She just wants to trick you!" Sun's voice could be heard yelling. (Y/n) determined that the source of the voice was indeed coming from the main entrance. If she could just get outside to Lunala...or better yet, get a message to Lunala.

       (Y/n) focused and thought very hard in order to get only Lunala to hear her thoughts. Neroza had taught her how to project her thoughts to a specific psychic type pokémon.

        "Lunala, if you're out there, I could use your help." There was no answer but (y/n) did hear Lunala's distant cosmic cry.

       "Well I guess your time is up, (y/n). One of your friends is going to have to go, but I wonder which one. Perhaps the unconscious Lillie or Hau. Maybe your precious pokémon? He is the only one out here since you still have his pokéball. That's what they're called right? Oh wait, no. Silvally is here too. That's this one's name isn't it? And let's not forget poor Sun who has to watch all of this happen," Moon said.

        Her friends were in danger and she had no idea what Moon planned on doing to her. She had to do something, but what?

        "I think I'll choose this one," Moon said getting an immediate response from Sun.

        "No! Leave him alone, please! Take me as your bargaining chip instead of (y/n), just don't hurt him!" Sun pleaded.

        "Now, now Sun. We discussed this on the way here. (Y/n) is the only one I need here. If she doesn't come out, the Hau here is going to have to pay the price," Moon said with mischief in her voice. As soon as she spoke, Lunala gave (y/n) an answer.

        "I'm on the way. Solgaleo has awaken now and can take care of Necrozma," Lunala's voice said in (y/n)'s mind. If that was the case then (y/n) could safely go and save Hau.

         "I give up! Just don't hurt Hau!" (y/n) said as she quickly stood up. Her laptop was on the floor but she kept her flash drive in her pocket. Moon was right outside of Aether Paradise holding Hau in a headlock. Sun was being held down by a mysterious psychic force that couldn't have been Necrozma.

        "Let him go," (y/n) said. Moon complied with her wishes and let Hau go who fell to the ground since he was still unconscious from earlier.

        "How did you get everyone here so quickly?" (y/n) inquired in an attempt to buy herself some time. She also wanted Moon to focus on her rather than Hau.

       "Rather than telling you, how about I show you," Moon said. In an instant, (y/n) was surrounded in the same odd energy that Sun was in and she was lifted into the air and pulled towards Moon.

        "You aren't just my bargaining chip. No, you're my key to reaching my goal. You alone can understand the true bond the a psychic type pokémon can have and you will teach me how to control it...or else, your friends and anyone that you might care about will suffer the consequences for your actions," Moon said.

       (Y/n) was frightened by what she was witnessing. Moon being able to weild psychic power to this degree was extraordinary but disturbing at the same time.

        "Cosmoem, take any information that I need from her," Moon said but there was no one else by the name of Cosmoem around. Then it hit her. The name of the pokémon that Nebby evolved into before becoming Lunala was called Cosmoem.

       According to what (y/n) knew about psychic type pokémon so far, they could conceal their presence by tricking someone's mind into thinking that they aren't even there, making them seem invisible. Cosmoem must have been doing this but (y/n) had nothing to worry about. Neroza had taught her how to keep her mind secure enough to break through any sort of psychic anomaly that could occur.

       Well, she thought she didn't have anything to worry about until she actually had to fight off the psychic attack. An excruciating headache suddenly showed up and (y/n) couldn't help but let out a cry of pain but she did not break. Her willpower alone was enough to keep Cosmoem's intrusion from succeeding. Then (y/n) head a familiar voice.

        "(Y/n)!!" Gladion said from behind her. He ran towards her but stopped once he got a better look at he situation.

       "Let (y/n) go!" Gladion growled at Moon. She simply glanced at him before returning her attention to (y/n).

        "You're more useful than I thought. If you can keep a mind attack like that one from working, then imagine what else you can do. I just need to figure out how to get that information out of you," Moon said. She then released (y/n) from her psychic hold and let Gladion take her place. As soon as (y/n) was released though, she put her plan into action.

       "Lunala!" she called. In an instant, Lunala swooped down and swiped at Moon who lost her psychic concentration. Lunala also restored the consciousness of those who had been unconscious minutes earlier by sending out a short psychic wave of energy.

        Necrozma, who had been fighting Solgaleo, quickly came to Moon's side but Lunala used Moongeist Beam and Solgaleo appeared and used Sunsteel Strike which Necrozma took the damage for.

       Moon was still in shock by what had just happened so (y/n) took the opportunity to finish the rest of her plan. Just as Moon stood up, (y/n) rushed forward and tackled her just as Lunala, who had read (y/n)'s mind, opened an ultra wormhole right behind Moon. Lunala was supposed to go in after (y/n) to bring her back just as planned but it didn't happen that way.

       Instead, Rei managed to make it to her since Lunala was hindered by a different pokémon. Necrozma hadn't fainted and teleported itself into Lunala's way, quickly using Photon Geyser which created a bright flash of light.

        (Y/n) couldn't keep her eyes open and the last thing she remembered before being knocked out by Moon was floating through ultraspace without knowledge of what would happen next.
____________________________________

Welp, that seems pretty bad. I guess we won't know what happens until next time you awesome readers!