I'm getting the feeling that "Master" is very much dead and Mute was Master's final creation for the sake of protecting her and because of that Mute knows Master is dead and gone so he just goes around with her and does his best to keep her happy...of course, considering it's a future world with high-tech to make humanoid robots that internally convert food into enough power to run on, it's possible he even uploaded a copy of his own mind into Mute at the end