Who is/are the one(s) responsible for creating the detective

[Davit08]

i've been wondering for a long time..i've been trying to google but no luck anyone mind helping me out? thanks alot

[Jd-]

The background music or the musicians doing the opening & ending themes?

If it's the BGM, that's Katsuo Oono (no relation to Yuji Oono of Lupin fame, sadly).

If it's the opening & ending themes, they are almost universally handled by Being Giza and their sub-labels. Most songs feature lyrics by the performers based on melodies, compositions, and arrangements by their in-house composers outside of a few exceptions (B'z operates out of their own sub-label where they have control, and BREAKERZ appears to handle their own song production as well).

[CarpetCrawler]

Generally, if you're talking about the BGM of the series, it's usually credited to the "Katsuo Ono Band".

EDIT: Looks like Jd- beat me to the punch... didn't know about how the opening and ending themes were chosen, though.

[Davit08]

THANKS SO MUCH MY GOOD FRIENDS! YOU GUYS ROCK! IDK HOW I CAN EVER REPAY YOU FOR YOUR TIME!