I'm trying to find an anime which has a boy detective or something similar, but he does his job not to help people but for the money. He has a girl assistant that controls a flying robot.
The boy has dark brown hair, hazel eyes and a uniform, kind of light brown, with a cap which has a symbol his brother gave to him.
There are comedy scenes where he and his assistant go in a weaponry shop to buy guns but they always get a discount. Also the end was about his assistant the girl, being a slave for experiments.
Can someone help me remember the name of it?