Definitely anime. I don't think you can really do two seasons, so I'd focus on maybe 13 episodes.
I think you can do a fairly straightforward type adaptation, however to do the final twist at the end, I would change the animation style into a rotoscoping type thing and turn it into a single-cam thing. Have her "pull" the camera to her and keep it on her. Have her comment on knowing she is in an anime, and my god if you can somehow program it in, have her read your account (let's say it is on Netflix) and have some banter set up about certain shows that you watched. "Oooo, you watched Stranger Things? I bet you it would be something that Natsuki really enjoyed. Yuri would have found something to complain about, but you and I can just watch it together forever if that's what you want, I'm not like them at all" Maybe take a cue from Eternal Darkness and have her start messing with the volume, or even unliking something on your Netflix account?
Man, that was partially what I was thinking. It would be cool if somehow she could "infect" your shows you try to watch until you "beat" her too, but that is something that we are far from being able to do, haha. I was thinking of how you capture that feeling of being "trapped" where you can't rewind/fast-forward/go back to previous episodes (and if you try to pause, she lets you know that you can't escape her even on the pause screen), and I think if it's on a format like Netflix, surely there would be a way to actually mimic that. In terms of escaping purgatory, now that, I don't know. I just would take issue with the viewer "escaping" her by just... letting the show run normally. Feels against the spirit of the game. In terms of keeping you there, a randomly generating A.I. algorithm that loops like the game, playing a random clip of her saying something doesn't feel out-of-the-realm-of-possibilities.
Of course, this is just me dreaming. I know it would be hard to actually implement such a thing, lol.
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