mars~

I'm looking for a manga(?). It should be pretty old, I think it was a survival game theme where the protagonist woke up with no memories (she had green-blue(?) hair) and was forced to kill. It was later revealed that she was originally one of the researchers who volunteered to undergo the experiment.

I think the name was something like black swamp/marsh, but I can't find anything about it.

And it might have been based on a videogame.

The main character was an actress for stage plays, and typically played the role of villain. Her 'rival' had blond hair (though I'm not too sure about that) and was popular, typically starring as the heroine. I don't remember if it was GL or not, and there might have been a psychological tag. I think the gist of the story was about the relationship of the two girls, though I don't remember if they were competing or cooperating.