There is a real lack of substance to the Michael and Tiara subplots compared to the Lina/Marvin - Care/Paul ones.

I wonder if Rainer intended Paul to get the game so he can be regressed back into Care.

If we take this to be true;

Could the Tiara being regressed into Belle be;

A. A test run of this regression software that went horribly wrong.

and

B. For Rainer to learn what happened with Mike (possibly his brother) back in 1995. Could the two kids we hear on the windmill camera tilt be a recording of Mike and Belle playing the game as kids. Could a tragedy occurred (with a car maybe) that Belle had some hand in. An accident that caused her trauma; enough trauma to be reborn through techniques like the real world Newmaker case and THIS is what gives Anna the same idea to do the same with Care following her kidnapping.

Belle became Tiara due to the trauma caused by Mike's death, she was meant to be regressed back into Belle.

Care became Paul due to the trauma caused by Her Kidnapping and Emotional Torture, he was successfully regressed back into Care.