[Thisguy]

Originally Posted by DingoEnderZOE2

For those who are curious check out the fight between Keichi and Rena with the Original BGM from the same fight from during the game:

http://youtube.com/watch?v=Abqj3W44Ikw

Nope, MODer applied wrong BGM for that one and he says so in the comment, although written in Japanese.
(彷徨いの言葉は天に導かれ is the BGM used in scene from Rika's headbutt to K's disarming the bomb)

http://www.youtube.com/watch?v=jm9NSTSH1LI
This is correct one, which features 見えない何かに怯える夜 - this theme was also used in watergun fight, obviously to give fights the same atmosphere.