Spent all of Friday night playing through the rest of this game!
I managed to guess some of the reveals after playing half-ways through the game, though I really didn't expect the reveals about Luna and Sigma. Those were kind of a shock. This game is awesome!
I actually think Luna's ending might be my favorite, and she might even be my favorite character, possibly because she is the only character that never betrayed Sigma. The fact that almost all the other characters would sometimes seemingly randomly betray him annoyed me a little.
So I always felt bad when I had to betray Luna to get all the endings...
Some other forum threads mentioned the game "Ever 17: The Out of Infinity" as a very good game in the similar style, written by the same head writer (Kotaro Uchikoshi). Anyone tried/heard of that game?