Someone mentioned earlier that, perhaps, this time travel story is following the show Dark, which I was unaware of before then, with its multiple time periods. So far, we have only interacted with the current time and 20 years past. The shit ninja affair seems to indicate a future time the story will cover. As the MC has only time traveled from the power plant to the power plant it is unusual for the shit ninja to appear in the school if they were time traveling, except if it was from the future where they now have control of time traveling and can go any where and any time. Plus the stun weapon used by shit ninja being able to push everyone away seems futuristic.
It does seem like it would be Darci to be the shit ninja since she loved the story about Selby getting hit with the garbage (which I don't think anyone else knew about other than Skylar, except Darci and Krystal), has trained in martial arts and likes ninjas. Though, Skylar could also be the shit ninja since she was the one to originally throw the garbage and has a lot of skill riding a skateboard giving some acrobatic ability. Personally, I think it's Darci because something bad may have happened in that scene with Shelby in the hallway and she goes back to 'fix' it and we only see the change, not the original event.
Overall, though, time traveling in the same timeline is very problematic and using that to solve problems or conflicts is kinda the modern day tale's use of the old Greek deus ex machina plot device.
It does seem like it would be Darci to be the shit ninja since she loved the story about Selby getting hit with the garbage (which I don't think anyone else knew about other than Skylar, except Darci and Krystal), has trained in martial arts and likes ninjas. Though, Skylar could also be the shit ninja since she was the one to originally throw the garbage and has a lot of skill riding a skateboard giving some acrobatic ability. Personally, I think it's Darci because something bad may have happened in that scene with Shelby in the hallway and she goes back to 'fix' it and we only see the change, not the original event.
Overall, though, time traveling in the same timeline is very problematic and using that to solve problems or conflicts is kinda the modern day tale's use of the old Greek deus ex machina plot device.