I too had the impression from the beginning Mitsuko was going to be the winner. The final duel was pure madness, btw... Regarding the true ending, with Mitsuko getting killed, while I thought she was going to be the winner, thinking about it, it was so obvious that she was going to survive, that it was probably a well pondered trick to make viewer think the same as you and me. I mean, all clues and hints made you think she wasn't really dead or that she was the final survivor. Anyway, that made you wonder about her till the very end.