yes yes exactly i was thinking about this too especially the part about loosing his tape to someone else i have so many thoughts hahhh
it feels a bit random tbh but also itd make sense. It might've also been doha's save point before Bada saw him insert the other tape, since itd explain doha acting shady early in the series and why Bada has bever found the tape player before.
this could mean tho that Bada was also always an "npc" and his memories of a past life were something he made up after being stuck here for so long (or at least thats what i think would be cool)
The game uses tapes as save points, so when you get something new done in an area you can insert the tape in a cassette player to save your progress.
As for the memory loss, my take is that probably if none of the tape players contain one of your saves, it counts as a fresh start, and you don't know youre even in a horror game anymore. It would explain why whats his face lost his save when Doha took the checkmarked tape out, since it seems he always used the same tape (the one he took from the guy in the car) to save. Having his one save taken out made him lose his whole run basically.
The end tape might be Doha's. No one but Doha and Bada is likely to go around messing with tapes, so realistically it's safe for Doha to have only 2 saves, his first one and (MAYBE) the end tape.
I think it'd make sense since we've seen Doha mess with the tape player there i think(?) plus I think Doha would totally write end on his tape in hopes that, even if Bada finds it, he'd feel too bad about possibly never seeing Doha again, he'd hesitate to use it.