Aren't the casettes different for each player that's why they need to find their own cassete and place their own tape for save?
In the current chapter, doha believes that the cassete he previously used was the glasses guy's which mean the glasses guy was using it behind mc's back but still the map didnt expand. Maps expand when you gather enough
It hasn’t been confirmed who is the player or who is the npc but saving the tape in the cassette does help them remember their previous game level. There are still some mystery to solve. I don’t think they have their own cassette. It’s kinda like treasure hunting, there is no individual cassette but you can form a team like doha and bada did.
But saving in a new casette doesnt expand the map too as we are now aware from the current chapter that while bada is doing his own thing, Glasses guy Used it too. Which means both casettes where used and nothing happened. Then when they(doha and bada) teamed up and explored enough a new map opened.
They have to find the cassette and play it (which is a game. for eg let’s say level 1) and after playing it, they need to save it so that can proceed with another level. There’s the time limit within which they need to find the cassette and save it. Finding game items will help them find the location of the cassette. If they don’t save the cassette after finding it, they will end up playing the same scenario again. Bada has now found the end cassette which is like the last level. So, when they reincarnated again, the end game started. Now they need to play it and then save it for the game to be over. But it seems the ML doesn’t want the game to end since it means bada and he will probably separate. Also, i believe if a player saves a cassette, they will realize they are inside the game once they reincarnates again.