I needed a stable, well-paying job so my brother wouldn't have anything to worry about -- I was going to take care of him. Since my father used to be in the force, I had a way to get in easier than I would otherwise.

So it was mostly out of pragmatism.

[It was mostly for Tatsuya's sake. There was also trying to find out the truth behind his father's dishonorable firing, but Tatsuya was the main reason why]