[Ataruman]

I don't mind Burai's face to heel turn because it was part of his character development. His biggest problem is that he doesn't want to let go of the past, particularly matters beyond his own control (the death of his father, Geki becoming a Yamato prince while he's essentially exiled) when there are more important things at hand such as dealing with Bandora or the whole "save the dinosaur eggs to secure our future...in way". His acceptance of the Sword of Helfriede and alliance with Bandora is because he is willing to do anything to defeat Geki all because of his priveledged life and everything he's been through, not realizing how hard Geki has had it and the sudden revelations he has that he's got an older brother and that he isn't legitimate outside the adoption in the Yamato prince position.

Ultimately the whole lesson of the Burai arc is to just "let his anger go", and he ultimately does that when he finally reconciles with Geki. He can't do it while working for Bandora, but does do so finally once he realizes that Geki does care and that he has a limited time left due to the circumstances that brought him back in the first place (associated with the Green Candle and the Time-Space Room). The issues with Geki are nothing compared to the greater issues at hand and its just something created in the past that has no baring on the possible future they have.