then a explosion happens in Reality B and destroys the servers where reality C was being simulated (and obviously reality D as well)

a guy in reality B who used to "dive" in reality C, only to "dive" in reality D and meet a NPC girl in reality D, and was in love with that NPC girl in reality D, goes crazy because he didn't have a backup, and reality C and reality D are gone forever, and he will never find the girl again

then a girl in reality A who likes to watch this guy in reality B decides to dive in reality B and convince the desperate guy that time travel is possible, and they both can time travel do before the explosion... she manipulates reality B to make that "time travel" possible (actually, a new simulation starting from a previous "Restore point") and takes the guy to before the explosion, so they both can enter reality C, and then enter reality D, where they engage in a threesome with the girl in reality D, then the movie becomes softcore porn