Same question, but i have some idea ^^:
i think it depends the dufficulty tou play.
If it is easy, you cansee that yau have only one choice when you must chose an answer, but when i finished the game in hard, i had some choice ( 2 choices each times i had to choose an answer) and when i killed the boss, after the credits, it said me something about L and R but i didn't understand ^^
Anyway i havn't sercret caractere. So if someone can help.
Now i am here, can comeone tell me how to save in Mill ?